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
exo 34:1THE TABLES ARE RENEWED. (Exo. 34:1-35)
the like unto the first--God having been reconciled to repentant Israel, through the earnest intercession, the successful mediation of Moses, means were to be taken for the restoration of the broken covenant. Intimation was given, however, in a most intelligible and expressive manner, that the favor was to be restored with some memento of the rupture; for at the former time God Himself had provided the materials, as well as written upon them. Now, Moses was to prepare the stone tables, and God was only to retrace the characters originally inscribed for the use and guidance of the people.
exo 34:2present thyself . . . to me in the top of the mount--Not absolutely the highest peak; for as the cloud of the Shekinah usually abode on the summit, and yet (Exo 34:5) it "descended," the plain inference is that Moses was to station himself at a point not far distant, but still below the loftiest pinnacle.
exo 34:3no man shall come up with thee . . . neither . . . flocks nor herds--All these enactments were made in order that the law might be a second time renewed with the solemnity and sanctity that marked its first delivery. The whole transaction was ordered so as to impress the people with an awful sense of the holiness of God; and that it was a matter of no trifling moment to have subjected Him, so to speak, to the necessity of re-delivering the law of the ten commandments.
exo 34:4Moses . . . took in his hand the two tables of stone--As Moses had no attendant to divide the labor of carrying them, it is evident that they must have been light, and of no great dimensions--probably flat slabs of shale or slate, such as abound in the mountainous region of Horeb. An additional proof of their comparatively small size appears in the circumstance of their being deposited in the ark of the most holy place (Exo 25:10).
exo 34:5the Lord descended in the cloud--After graciously hovering over the tabernacle, it seems to have resumed its usual position on the summit of the mount. It was the shadow of God manifest to the outward senses; and, at the same time, of God manifest in the flesh. The emblem of a cloud seems to have been chosen to signify that, although He was pleased to make known much about himself, there was more veiled from mortal view. It was to check presumption and engender awe and give a humble sense of human attainments in divine knowledge, as now man sees, but darkly.
exo 34:6the Lord passed by before him--in this remarkable scene, God performed what He had promised to Moses the day before.
proclaimed, The Lord . . . merciful and gracious--At an earlier period He had announced Himself to Moses, in the glory of His self-existent and eternal majesty, as "I am" [Exo 3:14]; now He makes Himself known in the glory of His grace and goodness--attributes that were to be illustriously displayed in the future history and experience of the church. Being about to republish His law--the sin of the Israelites being forgiven and the deed of pardon about to be signed and sealed by renewing the terms of the former covenant--it was the most fitting time to proclaim the extent of the divine mercy which was to be displayed, not in the case of Israel only, but of all who offend.
exo 34:8Moses bowed . . . and worshipped--In the East, people bow the head to royalty, and are silent when it passes by, while in the West, they take off their hats and shout.
exo 34:9he said, If now I have found grace in thy sight, O Lord, let my Lord, I pray thee, go among us--On this proclamation, he, in the overflowing benevolence of s heart, founded an earnest petition for the Divine Presence being continued with the people; and God was pleased to give His favorable answer to Moses' intercession by a renewal of His promise under the form of a covenant, repeating the leading points that formed the conditions of the former national compact.
exo 34:27And the Lord said unto Moses, Write thou these words--that is, the ceremonial and judicial injunctions comprehended above (Exo. 34:11-26); while the rewriting of the ten commandments on the newly prepared slabs was done by God Himself (compare Deu 10:1-4).
exo 34:28he was there with the Lord forty days and forty nights--as long as formerly [Exo 24:18], being sustained for the execution of his special duties by the miraculous power of God. A special cause is assigned for his protracted fast on this second occasion (Deu 9:18).
exo 34:29Moses wist not that the skin of his face shone while he talked with him--It was an intimation of the exalted presence into which he had been admitted and of the glory he had witnessed (Co2 3:18); and in that view, it was a badge of his high office as the ambassador of God. No testimonial needed to be produced. He bore his credentials on his very face; and whether this extraordinary effulgence was a permanent or merely temporary distinction, it cannot be doubted that this reflected glory was given him as an honor before all the people.
exo 34:30they were afraid to come nigh him--Their fear arose from a sense of guilt--the beaming radiance of his countenance made him appear to their awe-struck consciences a flaming minister of heaven.
exo 34:33he put a veil on his face--That veil was with the greatest propriety removed when speaking with the Lord, for every one appears unveiled to the eye of Omniscience; but it was replaced on returning to the people--and this was emblematic of the dark and shadowy character of that dispensation (Co2 3:13-14).