And, behold, I, even I, do bring a flood of waters upon the earth, to destroy all flesh, wherein is the breath of life, from under heaven; and every thing that is in the earth shall die.

Wesley's Notes

6:17 And behold, I, even I, do bring a flood of waters upon the earth - I that am infinite in power, and therefore can do it; infinite in justice, and therefore will do it.

Jamieson-Fausset-Brown Bible Commentary

17-22. And, behold, I, even I, do bring a flood-The repetition of the announcement was to establish its certainty (Ge 41:32). Whatever opinion may be entertained as to the operation of natural laws and agencies in the deluge, it was brought on the world by God as a punishment for the enormous wickedness of its inhabitants.

Matthew Henry's Concise Commentary

6:12-21 God told Noah his purpose to destroy the wicked world by water. The secret of the Lord is with them that fear him, Ps 25:14. It is with all believers, enabling them to understand and apply the declarations and warnings of the written word. God chose to do it by a flood of waters, which should drown the world. As he chooses the rod with which he corrects his children, so he chooses the sword with which he cuts off his enemies. God established his covenant with Noah. This is the first place in the Bible where the word 'covenant' is found; it seems to mean, 1. The covenant of providence; that the course of nature shall be continued to the end of time. 2. The covenant of grace; that God would be a God to Noah, and that out of his seed God would take to himself a people. God directed Noah to make an ark. This ark was like the hulk of a ship, fitted to float upon the waters. It was very large, half the size of St. Paul's cathedral, and would hold more than eighteen of the largest ships now used. God could have secured Noah without putting him to any care, or pains, or trouble; but employed him in making that which was to be the means to preserve him, for the trial of his faith and obedience. Both the providence of God, and the grace of God, own and crown the obedient and diligent. God gave Noah particular orders how to make the ark, which could not therefore but be well fitted for the purpose. God promised Noah that he and his family should be kept alive in the ark. What we do in obedience to God, we and our families are likely to have the benefit of. The piety of parents gets their children good in this life, and furthers them in the way to eternal life, if they improve it.