John Gill Commentary Luke 19:40

"And he answered and said, I tell you that, if these shall hold their peace, the stones will cry out." — Luke 19:40 (ASV)

And he answered and said to them, I tell you
As a truth, which may be depended on, and you may be assured of; this he spoke with great earnestness, fervour, and courage:

that if these should hold their peace ;
be silent, and not sing the praises of God, and ascribe glory to him, and profess the Messiah, and make this public acknowledgment of him:

the stones would immediately cry out ;
either against them, or in a declaration of the Messiah: by which expression our Lord means, that it was impossible it should be otherwise; it would be intolerable if it was not; and rather than it should not be, God, who is able out of stones to raise up children to Abraham, would make the stones speak, or turn stones into men, who should rise up and praise the Lord, and confess the Messiah; hereby commending his disciples, and tacitly reflecting upon the Pharisees, for their stupidity; and also giving a hint of the conversion of the Gentiles, who might be compared to stones, especially in the opinion of the Jews.