Charles Ellicott 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)

Which the Egyptians attempting to do.—Literally, Of which the Egyptians making an attempt were swallowed up (Exodus 14:15). In the same “trial,” but with the support of the word of God, Israel's faith had consisted. The word land is not in the ordinary Greek text (and therefore is in italics), but is found in the best manuscripts. The following clause (“of which . . .”) connects with this word.