Verse 16 repeats elements from the seven previous verses and emphasizes that all the actions taken by Noah were in obedience to God’s commands.

And they that entered: they again refers to the animals in verses 14-15. Entered means “entered the boat.”

Male and female of all flesh repeats in slightly different form “two and two of all flesh” from verse 15. Went in has already been stated in verses 9, 13, 15. As God had commanded is repeated from 6.22; 7.5, 9.

And the LORD shut him in: some interpreters believe these words originally stood after verse 10. Nevertheless they should be translated in their position in the text as we have it. And represents a further sequence of events and is better translated in English by “Then, After that, When all that was finished.” The LORD yahweh replaces “God” ʾelohim. Shut here conjunction refers to the action of closing the door with someone inside. That is, after Noah and the others were inside the boat, the LORD shut the door. Him refers to Noah as the one God had commanded and instructed. The LORD’s act of shutting the door behind Noah is to be understood as protecting Noah and not imprisoning him. Good News Translation uses a separate sentence: “Then the LORD shut the door behind Noah.” We may also say, for example, “When Noah was inside the boat, the LORD shut the door” or “After Noah went inside the boat, the LORD closed the boat’s door.”

Quoted with permission from Reyburn, William D. and Fry, Euan McG. A Handbook on Genesis. (UBS Helps for Translators). New York: UBS, 1997. For this and other handbooks for translators see here .