Verse 6:[1] Moreover he said, (Gen. 28:13; Ex. 3:15; 4:5; Matt. 22:32; Mark 12:26; Luke 20:37; Acts 7:32) I am the God of thy father, the God of Abraham, the God of Isaac, and the God of Jacob. And Moses hid his face; for (so 1 Kings 19:13; Is. 6:1, 5) he was afraid to look upon God.
[I am, etc.] This is wanting in Hebrew, likewise in Mark 12:26, but it is supplemented in Matthew 22:32[2] (Ainsworth).
[The God of Abraham, the God of Isaac, the God of Jacob] That is, whom they worshipped. He names these because they were the founders of the Hebrew nation, and to these God promised and fulfilled a great many things, and they were superior with respect to virtue. Thus He distinguishes Himself from false gods, and renews the memory of the covenant entered into with their fathers, upon which the liberation of Israel depends (Junius, Piscator). It is repeated three times; by which they maintain to be signified what sort of care God has of individuals, and that He is wholly God to each one (Menochius).
The God of thy fathers, engaged to them by covenant or promise, which I am now come to perform.
[He hid his face] Out of reverence for God (Menochius, Lyra, Ainsworth), and out of a sense of his own infirmity (Ainsworth), and out of humility; now, he does not thrust himself forward curiously: and therefore God revealed Himself to him (Lyra).
He was afraid to look upon God, as other excellent servants of God have been, through the sense of their own meanness and sinfulness, and of God’s majesty and holiness. See Genesis 16:13; 17:3; 1 Kings 19:13; Isaiah 6:2, 5, etc.
[1] Hebrew: וַיֹּ֗אמֶר אָנֹכִי֙ אֱלֹהֵ֣י אָבִ֔יךָ אֱלֹהֵ֧י אַבְרָהָ֛ם אֱלֹהֵ֥י יִצְחָ֖ק וֵאלֹהֵ֣י יַעֲקֹ֑ב וַיַּסְתֵּ֤ר מֹשֶׁה֙ פָּנָ֔יו כִּ֣י יָרֵ֔א מֵהַבִּ֖יט אֶל־הָאֱלֹהִֽים׃
[2] Matthew 22:32a: “I am (εἰμι) the God of Abraham…”