A.T. Robertson Commentary Luke 23:31

"For if they do these things in the green tree, what shall be done in the dry?" — Luke 23:31 (ASV)

In the green tree (εν υγρω ξυλω). Green wood is hard to burn and so is used for the innocent.

In the dry (εν τω ξηρω). Dry wood kindles easily and is a symbol for the guilty. This common proverb has various applications. Here the point is that if they can put Jesus to death, being who he is, what will happen to Jerusalem when its day of judgment comes?

What shall be done (τ γενητα). Deliberative subjunctive.