Isaiah 36:6

Lo, thou trustest in the staff of this broken reed, on Egypt,
&c.] His ally and auxiliary; and which is rightly called "the staff of a broken reed", if trusted to, and leaned upon, being weak and frail, and an insufficient ground of confidence to depend upon; the allusion seems to be to the cane or reed which grew upon the banks of the river Nile, in Egypt: whereon if a man lean, it will go into his hand, and pierce it;
the splinters of the broken reed being leaned on, will enter into a man's hand, and do him harm, instead of being a help to him to walk with: so is Pharaoh king of Egypt to all that trust in him;
pernicious and harmful, instead of being useful and helpful.