She could not longer hide him, with safety to herself, because they now grew more violent in executing that bloody decree, and the child growing up was more likely to be discovered, especially seeing the Egyptians dwelt among them, Exodus 3:22. That boats were made of such materials as bulrushes in those parts, is evident from Isaiah 18:2, and from the testimonies of Herod, Pliny, and others. Slime and pitch; slime within, and pitch without. She hid it in the flags, which grew near the river's side; partly that the vessel might not be carried away, and overturned by the violence of the winds and water, and partly that the child might be sooner discerned, and more easily taken out thence by any kind hand, which she hoped for.
Related Commentaries of Exodus 2:3
Exodus 2:3
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.