Then the LORD saw that the wickedness of man was great in the earth, and that every intent of the thoughts of his heart was only evil continually. And the LORD was sorry that He had made man on the earth, and He was grieved in His heart. So the LORD said, "I will destroy man whom I have created from the face of the earth, both man and beast, creeping thing and birds of the air, for I am sorry that I have made them." But Noah found grace in the eyes of the LORD. (Genesis 6:5-8, NKJV)
The word for repentance here conveys the idea of heavy breathing as in panting or sighing. It depends on the context. If it is to be understood as something good, then it will be translated comfort, etc. If the context is something negative, then it will be translated as being sorry, change the mind, etc.
In a good sense:
- 1 Chronicles 7:22
- Isaiah 40:1
- Zechariah 1:17
In a bad sense:
- Genesis 6:6
- Job 42:6
- Jeremiah 20:16
The basic sense, again, is an emotional change of mind, thus comfort, repent, be sorry for, etc.
So God did not commit a sin that He needed to repent, that is, change of character, rather it was an emotion of seeing things good and happy about it to seeing this evil and being sad about it.
K&D has "The force of יִנָּחֵם (nâcham), "it repented the Lord," may be gathered from the explanatory יִתְעַצֵּב` (atsab), "it grieved Him at His heart." This shows that the repentance of God does not presuppose any variableness in His nature of His purposes. In this sense God never repents of anything (1 Samuel 15:29), "quia nihil illi inopinatum vel non praevisum accidit" (Calvin). The repentance of God is an anthropomorphic expression for the pain of the divine love at the sin of man, and signifies that "God is hurt no less by the atrocious sins of men than if they pierced His heart with mortal anguish" (Calvin). The destruction of all, "from man unto beast," etc., is to be explained on the ground of the sovereignty of man upon the earth, the irrational creatures being created for him, and therefore involved in his fall. This destruction, however, was not to bring the human race to an end. "Noah found grace in the eyes of the Lord." In these words mercy is seen in the midst of wrath, pledging the preservation and restoration of humanity." Keil & Delitzsch Commentary on the Old Testament on Genesis 6:6.
Another comment: "A peculiarly strong anthropathic expression, which, however, presents the truth that God, in consistency with his immutability, assumes a changed position in respect to changed man" (Lange). That he had made man on the earth. i.e. that he had created man at all, and in particular that he had settled him on the earth. And it grieved him at his heart. A touching indication that God did not hate man, and a clear proof that, though the Divine purpose is immutable, the Divine nature is not impassible." Pulpit Commentary on Genesis 6:6.