A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
isa 6:1VISION OF JEHOVAH IN HIS TEMPLE. (Isa 6:1-13)
In . . . year . . . Uzziah died--Either literal death, or civil when he ceased as a leper to exercise his functions as king [Chaldee], (Ch2 26:19-21). 754 B.C. [CALMET] 758 (Common Chronology). This is not the first beginning of Isaiah's prophecies, but his inauguration to a higher degree of the prophetic office: Isa 6:9, &c., implies the tone of one who had already experience of the people's obstinacy.
Lord--here Adonai, Jehovah in Isa 6:5; Jesus Christ is meant as speaking in Isa 6:10, according to Joh 12:41. Isaiah could only have "seen" the Son, not the divine essence (Joh 1:18). The words in Isa 6:10 are attributed by Paul (Act 28:25-26) to the Holy Ghost. Thus the Trinity in unity is implied; as also by the thrice "Holy" (Isa 6:3). Isaiah mentions the robes, temple, and seraphim, but not the form of God Himself. Whatever it was, it was different from the usual Shekinah: that was on the mercy seat, this on a throne; that a cloud and fire, of this no form is specified: over that were the cherubim, over this the seraphim; that had no clothing, this had a flowing robe and train.
isa 6:2stood--not necessarily the posture of standing; rather, were in attendance on Him [MAURER], hovering on expanded wings.
the--not in the Hebrew.
seraphim--nowhere else applied to God's attendant angels; but to the fiery flying (not winged, but rapidly moving) serpents, which bit the Israelites (Num 21:6), called so from the poisonous inflammation caused by their bites. Seraph is to burn; implying the burning zeal, dazzling brightness (Kg2 2:11; Kg2 6:17; Eze 1:13; Mat 28:3) and serpent-like rapidity of the seraphim in God's service. Perhaps Satan's form as a serpent (nachash) in his appearance to man has some connection with his original form as a seraph of light. The head of the serpent was the symbol of wisdom in Egypt (compare Num 21:8; Kg2 18:4). The seraphim, with six wings and one face, can hardly be identified with the cherubim, which had four wings (in the temple only two) and four faces (Eze 1:5-12). (But compare Rev 4:8). The "face" and "feet" imply a human form; something of a serpentine form (perhaps a basilisk's head, as in the temples of Thebes) may have been mixed with it: so the cherub was compounded of various animal forms. However, seraph may come from a root meaning "princely," applied in Dan 10:13 to Michael [MAURER]; just as cherub comes from a root (changing m into b), meaning "noble."
twain--Two wings alone of the six were kept ready for instant flight in God's service; two veiled their faces as unworthy to look on the holy God, or pry into His secret counsels which they fulfilled (Exo 3:6; Job 4:18; Job 15:15); two covered their feet, or rather the whole of the lower parts of their persons--a practice usual in the presence of Eastern monarchs, in token of reverence (compare Eze 1:11, their bodies). Man's service a fortiori consists in reverent waiting on, still more than in active service for, God.
isa 6:3(Rev 4:8). The Trinity is implied (on "Lord," see on Isa 6:1). God's holiness is the keynote of Isaiah's whole prophecies.
whole earth--the Hebrew more emphatically, the fulness of the whole earth is His glory (Psa 24:1; Psa 72:19).
isa 6:4posts of . . . door--rather, foundations of the thresholds.
smoke--the Shekinah cloud (Kg1 8:10; Eze 10:4).
isa 6:5undone-- (Exo 33:20). The same effect was produced on others by the presence of God (Jdg 6:22; Jdg 13:22; Job 42:5-6; Luk 5:8; Rev 1:17).
lips--appropriate to the context which describes the praises of the lips, sung in alternate responses (Exo 15:20-21; Isa 6:3) by the seraphim: also appropriate to the office of speaking as the prophet of God, about to be committed to Isaiah (Isa 6:9).
seen--not strictly Jehovah Himself (Joh 1:18; Ti1 6:16), but the symbol of His presence.
isa 6:6unto me--The seraph had been in the temple, Isaiah outside of it.
live coal--literally, "a hot stone," used, as in some countries in our days, to roast meat with, for example, the meat of the sacrifices. Fire was a symbol of purification, as it takes the dross out of metals (Mal 3:2-3).
the altar--of burnt offering, in the court of the priests before the temple. The fire on it was at first kindled by God (Lev 9:24), and was kept continually burning.
isa 6:7mouth . . . lips--(See on Isa 6:5). The mouth was touched because it was the part to be used by the prophet when inaugurated. So "tongues of fire" rested on the disciples (Act 2:3-4) when they were being set apart to speak in various languages of Jesus.
iniquity--conscious unworthiness of acting as God's messenger.
purged--literally, "covered," that is, expiated, not by any physical effect of fire to cleanse from sin, but in relation to the altar sacrifices, of which Messiah, who here commissions Isaiah, was in His death to be the antitype: it is implied hereby that it is only by sacrifice sin can be pardoned.
isa 6:8I . . . us--The change of number indicates the Trinity (compare Gen 1:26; Gen 11:7). Though not a sure argument for the doctrine, for the plural may indicate merely majesty, it accords with that truth proved elsewhere.
Whom . . . who--implying that few would be willing to bear the self-denial which the delivering of such an unwelcome message to the Jews would require on the part of the messenger (compare Ch1 29:5).
Here am I--prompt zeal, now that he has been specially qualified for it (Isa 6:7; compare Sa1 3:10-11; Act 9:6).
isa 6:9Hear . . . indeed--Hebrew, "In hearing hear," that is, Though ye hear the prophet's warnings again and again, ye are doomed, because of your perverse will (Joh 7:17), not to understand. Light enough is given in revelation to guide those sincerely seeking to know, in order that they may do, God's will; darkness enough is left to confound the wilfully blind (Isa 43:8). So in Jesus' use of parables (Mat 13:14).
see . . . indeed--rather, "though ye see again and again," yet, &c.
isa 6:10Make . . . fat-- (Psa 119:17). "Render them the more hardened by thy warnings" [MAURER]. This effect is the fruit, not of the truth in itself, but of the corrupt state of their hearts, to which God here judicially gives them over (Isa 63:17). GESENIUS takes the imperatives as futures. "Proclaim truths, the result of which proclamation will be their becoming the more hardened" (Rom 1:28; Eph 4:18); but this does not so well as the former set forth God as designedly giving up sinners to judicial hardening (Rom 11:8; Th2 2:11). In the first member of the sentence, the order is, the heart, ears, eyes; in the latter, the reverse order, the eyes, ears, heart. It is from the heart that corruption flows into the ears and eyes (Mar 7:21-22); but through the eyes and ears healing reaches the heart (Rom 10:17), [BENGEL]. (Jer 5:21; Eze 12:2; Zac 7:11; Act 7:57; Ti2 4:4). In Mat 13:15, the words are quoted in the indicative, "is waxed gross" (so the Septuagint), not the imperative, "make fat"; God's word as to the future is as certain as if it were already fulfilled. To see with one's eyes will not convince a will that is opposed to the truth (compare Joh 11:45-46; Joh 12:10-11). "One must love divine things in order to understand them" [PASCAL].
be healed--of their spiritual malady, sin (Isa 1:6; Psa 103:3; Jer 17:14).
isa 6:11how long--will this wretched condition of the nation being hardened to its destruction continue?
until-- (Isa 5:9) --fulfilled primarily at the Babylonish captivity, and more fully at the dispersion under the Roman Titus.
isa 6:12(Kg2 25:21).
forsaking--abandonment of dwellings by their inhabitants (Jer 4:29).
isa 6:13and it shall return, and . . . be eaten--Rather, "but it shall be again given over to be consumed": if even a tenth survive the first destruction, it shall be destroyed by a second (Isa 5:25; Eze 5:1-5, Eze 5:12), [MAURER and HORSLEY]. In English Version, "return" refers to the poor remnant left in the land at the Babylonish captivity (Kg2 24:14; Kg2 25:12), which afterwards fled to Egypt in fear (Kg2 25:26), and subsequently returned thence along with others who had fled to Moab and Edom (Jer 40:11-12), and suffered under further divine judgments.
tell--rather, "terebinth" or "turpentine tree" (Isa 1:29).
substance . . . when . . . cast . . . leaves--rather, "As a terebinth or oak in which, when they are cast down (not 'cast their leaves,' Job 14:7), the trunk or stock remains, so the holy seed (Ezr 9:2) shall be the stock of that land." The seeds of vitality still exist in both the land and the scattered people of Judea, waiting for the returning spring of God's favor (Rom 11:5, Rom 11:23-29). According to Isaiah, not all Israel, but the elect remnant alone, is destined to salvation. God shows unchangeable severity towards sin, but covenant faithfulness in preserving a remnant, and to it Isaiah bequeaths the prophetic legacy of the second part of his book (the fortieth through sixty-sixth chapters).
In the Assyrian inscriptions the name of Rezin, king of Damascus, is found among the tributaries of Tiglath-pileser, of whose reign the annals of seventeen years have been deciphered. For the historical facts in this chapter, compare 2Ki. 15:37-16:9. Rezin of Syria and Pekah of Israel, as confederates, advanced against Jerusalem. In the first campaign they "smote Ahaz with a great slaughter" (Ch2 28:5). Their object was probably to unite the three kingdoms against Assyria. Egypt seems to have favored the plan, so as to interpose these confederate kingdoms between her own frontier and Assyria (compare Isa 7:18, "Egypt"; and Kg2 17:4, Hoshea's league with Egypt). Rezin and Pekah may have perceived Ahaz' inclination towards Assyria rather than towards their own confederacy; this and the old feud between Israel and Judah (Kg1 12:16) occasioned their invasion of Judah. Ahaz, at the second inroad of his enemies (compare 2Ch. 28:1-26 and Kg2 15:37, with Isa 16:5), smarting under his former defeat, applied to Tiglath-pileser, in spite of Isaiah's warning in this chapter, that he should rather rely on God; that king accordingly attacked Damascus, and slew Rezin (Kg2 16:9); and probably it was at the same time that he carried away part of Israel captive (Kg2 15:29), unless there were two assaults on Pekah--that in Kg2 15:29, the earlier, and that in which Tiglath helped Ahaz subsequently [G. V. SMITH]. Ahaz was saved at the sacrifice of Judah's independence and the payment of a large tribute, which continued till the overthrow of Sennacherib under Hezekiah (Isa 37:37; Kg2 16:8, Kg2 16:17-18; Ch2 28:20). Ahaz' reign began about 741 B.C., and Pekah was slain in 738 [WINER].