Luke 23:30,31 - Joseph Benson’s Commentary on the Old and New Testaments

Then shall they begin to say to the mountains, Fall on us, &c. Proverbial expressions, to signify their desire of any shelter or refuge; and so very desirous were they of hiding themselves, that some thousands of them crept even into the common sewers, and there miserably perished, or were dragged out to slaughter. (Bell., Luke 6:9.) For if they do these things in a green tree, what shall be done in the dry If the Romans are permitted by Heaven to inflict such heavy punishments on me, who am innocent, how dreadful must the vengeance be which they shall inflict on the nation, whose sins cry aloud to heaven, hastening the pace of the divine judgments, and rendering the perpetrators as fit for punishments as dry wood is for burning. The expression is proverbial; and was in frequent use among the Jews, who compared a good man to a green tree, and a bad man to a dead and dry one. It is as if our Lord had said, If a righteous person suffer thus, what will become of the wicked? Of those who are as ready for destruction, as dry wood is for the fire? Compare Ezekiel 20:47, with Ezekiel 21:3, where God's burning every green and every dry tree is explained to be, his destroying the righteous and the wicked together. See also Psalms 1:3, where a good man is compared to a green tree full of leaves: and both Christ and John the Baptist resemble bad men to dry, dead, and barren trees.