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
psa 84:1(See on Psa 8:1, title, and Psa 42:1, title). The writer describes the desirableness of God's worship and prays for a restoration to its privileges. (Psa 84:1-12)
amiable--not lovely, but beloved.
tabernacles-- (Psa 43:3).
psa 84:2longeth--most intensely (Gen 31:30; Psa 17:12).
fainteth--exhausted with desire.
courts--as tabernacles (Psa 84:1) --the whole building.
crieth out--literally, "sings for joy"; but here, and Lam 2:19, expresses an act of sorrow as the corresponding noun (Psa 17:1; Psa 61:2).
heart and . . . flesh--as in Psa 63:1.
psa 84:3thine altars--that is, of burnt offering and incense, used for the whole tabernacle. Its structure afforded facilities for sparrows and swallows to indulge their known predilections for such places. Some understand the statement as to the birds as a comparison: "as they find homes, so do I desire thine altars," &c.
psa 84:4This view is favored by the language here, which, as in Psa 15:1; Psa 23:6, recognizes the blessing of membership in God's family by terms denoting a dwelling in His house.
psa 84:5(Compare Psa 68:28).
in whose heart . . . the ways--that is, who knows and loves the way to God's favor (Pro 16:17; Isa 40:3-4).
psa 84:6valley of Baca--or, "weeping." Through such, by reason of their dry and barren condition, the worshippers often had to pass to Jerusalem. As they might become wells, or fountains, or pools, supplied by refreshing rain, so the grace of God, by the exercises of His worship, refreshes and revives the hearts of His people, so that for sorrows they have "rivers of delight" (Psa 36:8; Psa 46:4).
psa 84:7The figure of the pilgrim is carried out. As such daily refit their bodily strength till they reach Jerusalem, so the spiritual worshipper is daily supplied with spiritual strength by God's grace till he appears before God in heaven.
appeareth . . . God--the terms of the requisition for the attendance on the feasts (compare Deu 16:16),
psa 84:9God is addressed as a shield (compare Psa 84:11).
thine anointed--David (Sa1 16:12).
psa 84:10I had . . . doorkeeper--literally, "I choose to sit on the threshold," the meanest place.
psa 84:11As a sun God enlightens (Psa 27:1); as a shield He protects.
grace--God's favor, its fruit--
glory--the honor He bestows.
uprightly-- (Psa 15:2; Psa 18:23).
psa 84:12that trusteth--constantly.