Verses with the word flags in the Old Testament (3 verses):

Exodus 2:3
And when she could not longer hide him, she took for him an ark of bulrushes, and daubed it with slime and with pitch, and put the child therein; and she laid it in the flags by the river's brink.

Exodus 2:5
And the daughter of Pharaoh came down to wash herself at the river; and her maidens walked along by the river's side; and when she saw the ark among the flags, she sent her maid to fetch it.

Isaiah 19:6
And they shall turn the rivers far away; and the brooks of defence shall be emptied and dried up: the reeds and flags shall wither.