For the phrase “Out of the mouths of babes and infants you have founded a bulwark because of your foes, to silence the enemy and the avenger,” see Matthew 21:16.

Note that this quote in the New Testament is not taken from the Hebrew Bible but from the Greek Septuagint (LXX) which translates into English as “Out of mouths of infants and nurslings you furnished praise for yourself, for the sake of your enemies, to put down enemy and avenger.'” (Translation by NETS — for the Greek version see the title’s tooltip)

See also out of the mouth of babes and sucklings.