From Book of Genesis: Chapters 1-17, Victor P. Hamilton, New International Commentary on the Old Testament.
Viewing the debacle man has fomented, God is grieved, even to the point of experiencing pain in his heart. Note again here the echo of earlier language in Genesis. Previously Eve (3:16) and Adam (3:17) were the pain bearers. Now Yahweh himself feels that stab. Eve’s and Adam’s pain, however, is imposed due to their sin. Yahweh’s is not. Rather, his pain finds its source in the depth of the regret he experiences over fallen humanity, and in the fact that he must judge such fallenness. It is easy, of course, to dismiss such allusions as anthropopathisms, and to feel that they can tell us nothing about the essential nature of God. But verses like this remind us that the God of the OT is not beyond the capability of feeling pain, chagrin, and remorse. To call him the Impassible Absolute is but part of the truth. Yahweh regretted [yinnāḥem] that he had made man. This point is made again in v. 7b, “I regret [ʾemḥeh] that I made him.” The AV translates nḥm as “repent.” Here we are introduced to the idea of God repenting! As a matter of fact, the Niphal of the root nḥm (as here) occurs forty-eight times in the OT, and in thirty-four of these the subject (expressed or implied) is God.3 Interestingly, the LXX usually translates Heb. nāḥam with metanoéō or metamélomai, “to be sorry, repent, change one’s mind,” but here and in v. 7 it avoids either of those verbs. It reads “And God considered that he had made man” (v. 6) and “because I have become angry that I made them” (v. 7).4 Here the LXX translators hesitated to have God repenting. The Hebrew root in question (nḥm) is related to the noun neḥāmá, “breath” (Ps. 119:50; Job 6:10), which describes the life-giving effect of God’s word in a time of oppression. The Niphal and Hithpael stems have six basic meanings: (1) suffer emotional pain (Gen. 6:6); (2) be comforted (Gen. 37:35); (3) execute wrath (Isa. 1:24); (4) retract punishment (Jer. 18:7–8); (5) retract blessing (Jer. 18:9–10); (6) retract (a life of) sin (Jer. 8:5–6).5 It should be noted that only a few passages that speak of God’s repentance refer to God repenting over something already done. The vast majority of the instances of Yahweh’s nḥm have to do with his possible change of will concerning a future plan of action.6 This is one significant difference between God’s repentance and man’s. Still, the fact that the OT affirms that God does repent, even over a fait accompli, forces us to make room in our theology for the concepts of both the unchangeability of God and his changeability.
secondary source: Chris Fisher (godisopen).