Jamieson, Fausset and Brown on Exodus 14:22

22. the children of Israel went into the midst of the sea, &c.--It is highly probable that Moses, along with Aaron, first planted his footsteps on the untrodden sand, encouraging the people to follow him without fear of the treacherous walls; and when we take into account the multitudes that followed him, the immense number who through infancy and old age were incapable of hastening their movements, together with all the appurtenances of the camp, the strong and steadfast character of the leaders' faith was strikingly manifested (Jos 2:10; 4:23; Psa 66:6; 74:13; 106:9; 136:13; Is 63:11-13; 1Co 10:1; He 11:29).