Genesis 7:9 (BSB)

came to Noah to enter the ark, two by two, male and female, as God had commanded Noah.

From Genesis 7. Also in the ESV.

Commentary on Genesis 7:9

• Matthew Henry (Presbyterian), Matthew Henry's Complete Commentary on Genesis 7:5-10: Here is Noah's ready obedience to the commands that God gave him. Observe, 1. He went into the ark, upon notice that the flood would come after seven days, though probably as yet there appeared no visible sign of its approach, no cloud arising that threatened it, nothing done towards it, but all continued serene and clear; for, as he prepared the ark by faith...
• John Gill (Reformed Baptist), Exposition of the Old and New Testaments on Genesis 7:9: And it came to pass after seven days,.... Were ended, or on the seventh day, after God had given the orders to Noah, to prepare for his going into the ark, with his family, and all the creatures: that the waters of the flood were upon the earth: that is, they began to be upon the earth; for it continued to rain from hence forty...
• Jamieson-Fausset-Brown (Reformed), Commentary Critical and Explanatory on the Whole Bible on Genesis 7:9: There went in two and two--Doubtless they were led by a divine impulse. The number would not be so large as at first sight one is apt to imagine. It has been calculated that there are not more than three hundred distinct species of beasts and birds, the immense varieties in regard to form, size, and color being traceable to the influence of climate and other circumstances.
• Geneva Bible Notes (Reformed), Geneva Bible Study Notes on Genesis 7:9: There went in two and two unto Noah into the ark, the male and the female, as God had commanded Noah. (c) God compelled them to present themselves to Noah, as they did before to Adam, when he gave them names, .