Charles Ellicott Commentary Exodus 34:6

"And Jehovah passed by before him, and proclaimed, Jehovah, Jehovah, a God merciful and gracious, slow to anger, and abundant in lovingkindness and truth," — Exodus 34:6 (ASV)

The Lord passed by before him. — In this brief phrase we have the entire historical narrative of the manifestation of God’s glory to Moses. For details, we must refer to the terms of the promise (Exodus 33:21–23), which are also characterized by brevity but still add something to the bare statements of the present passage. Moses was, no doubt, hidden and protected by God’s hand in a clift of the rock while God’s glory passed by. He was only allowed to look out from his hiding-place after the glory had passed, when he saw the remains of it—the back parts; even this, however, was so brilliant a vision that it left a permanent light upon his countenance, which he ordinarily felt compelled to conceal from the people by means of a veil (Exodus 34:29–35).

The Lord, The Lord God... The new “name” of God is not a “name,” as we understand the expression; it is rather a description of His nature by means of a series of epithets. At the bush, He had revealed His eternal, self-existent character; in the descent on Sinai (Exodus 19:16–19; Exodus 20:18–21), He had shown His terribleness; now, in the act of pardoning His people and taking them once more into favour, He made known His attribute of mercy.

To further impress upon Israel this feature of His character, He accumulated epithet on epithet, calling Himself Rakhum, “the tender or pitiful one”; Khannun, “the kind or gracious one,” who bestows His benefits out of mere favour; Erek appayim, “the long-suffering one”; Rab khesed, “the great in mercy”; Notser khesed, “the keeper of mercy”; and Nose ’avon, “the forgiver of iniquity.”

Still, to prevent the fatal misapprehension that He is a Being of pure and mere benevolence (Butler, Analogy, Part I.,Exodus 2:0, p. 41), He added, to complete the description, a reference to His justice. He will by no means clear the guilty , and will visit iniquity to the third and fourth generation .