Psalm 8:2
1 For the music director, according to the gittith style; a psalm of David. O Lord, our Lord, how magnificent is your reputation throughout the earth! You reveal your majesty in the heavens above. 2 From the mouths of children and nursing babies you have ordained praise on account of your adversaries, so that you might put an end to the vindictive enemy. 3 When I look up at the heavens, which your fingers made, and see the moon and the stars, which you set in place, 4 Of what importance is the human race, that you should notice them? Of what importance is mankind, that you should pay attention to them?
Matthew 21:16
14 The blind and lame came to him in the temple courts, and he healed them. 15 But when the chief priests and the experts in the law saw the wonderful things he did and heard the children crying out in the temple courts, “Hosanna to the Son of David,” they became indignant 16 and said to him, “Do you hear what they are saying?” Jesus said to them, “Yes. Have you never read, ‘Out of the mouths of children and nursing infants you have prepared praise for yourself’?” 17 And leaving them, he went out of the city to Bethany and spent the night there. 18 Now early in the morning, as he returned to the city, he was hungry.
Notes and References
"... In all likelihood, Matthew’s insertion of material related to Psalm 8:2 stemmed from his understanding of children’s open receptiveness to spiritual concepts. Earlier in the Gospel he reveals this inclination with the statement, “At that time Jesus said, ‘I praise You, Father, Lord of heaven and earth, that You have hidden these things from the wise and intelligent’” referring to the scribes and chief priests, “and have revealed them to infants.” (Matthew 11:25, but see also 10:42 and 18:3–5). Frequently in the literature on Matthew 21:16, scholars eagerly note that Jesus’ words depend on the Septuagint’s rendition of the Hebrew Bible. Instead of an expected Greek equivalent to the Hebrew זֹע, such as δύναμις, indicating “strength” or “power,” Matthew chooses the word αἶνος, representing “praise.” Although it apparently deviates from a plain reading of the Hebrew text, it is nevertheless in line with the later Reed Sea tradition that recognizes praise stemming from the lips of the young ones ..."
Emanuel, David "Matthew 21:16: 'From the Lips of Infants and Babes' - The Interpretation of Psalm 8:2 in Matthew 21:16" in Notley, R. Steven (ed.) The Gospels in First-Century Judaea: Proceedings of the Inaugural Conference of Nyack College’s Graduate Program in Ancient Judaism and Christian Origins (pp. 44-57) Brill, 2016