Albert Barnes Commentary Hebrews 11:29

"By faith they passed through the Red sea as by dry land: which the Egyptians assaying to do were swallowed up." — Hebrews 11:29 (ASV)

By faith they passed through the Red sea as by dry land (Exodus 14:22, 29). That is, it was only by confidence in God that they were able to do this. It was not by any power they had to remove the waters and make a passage for themselves, nor was it by the operation of any natural causes. It is not to be supposed that all who passed through the Red Sea had saving faith. The apostle's assertion is that the passage was made in virtue of strong confidence in God; if it had not been for this confidence, the passage could not have been made at all. Of this no one can entertain a doubt who reads the history of that remarkable transaction.

Which the Egyptians assaying to do, were drowned (Exodus 14:27, 28). It is evidently referred to here to show the effects of not having faith in God, and of what would have inevitably befallen the Israelites if they had had no faith. The destruction of the Egyptians by the return of the waters, in accordance with natural laws, showed that the Israelites would have been destroyed in the passage if a divine energy had not been employed to prevent it. On the passage through the Red Sea, see Robinson's Biblical Researches, Volume 1, pages 81–86.