Luke 19:40

ἐὰν σιωπήσουσιν : ἐὰν with future indicative instead of subjunctive as in classic Greek, one of the divergent ways in which the N.T. expresses a future supposition with some probability (vide Burton, M. and T., §§ 250 256). οἱ λίθοι κράξουσιν, the stones will cry out; possibly there is a reference to Habakkuk 2:11, but the expression is proverbial (instances in Pricaeus, Wetstein, etc.) = the impossible will happen rather than the Messianic kingdom fail of recognition. Some, e.g., Stier and Nösgen, find in the words a reference to the destruction of the temple and the witness it bore to Jesus = if I receive not witness from the Jewish people the scattered stones of the ruined temple will witness for me. An attractive idea, not refuted by Hahn's objection that if it had been in view we should have had ὅταν οὗτοι σιωπ. instead of ἐὰν, etc. ἐὰν with future may express a future supposition with some probability.