Albert Barnes on Matthew 10:15

It shall be more tolerable for Sodom, etc. The cities here mentioned, together with Admah and Zeboim, were destroyed by fire and brimstone, or by a volcanic eruption, on account of their great wickedness. They occupied the place afterwards covered by the Dead Sea, bounding Palestine on the south-east, Gen 19:24,25. Christ said that their punishment will be more tolerable--that is, more easily borne--than that of the people who reject his gospel, The reason is, that they were not favoured with so much light and instruction. See Mt 11:23,24, Lk 12:47,48. Sodom and Gomorrah are often referred to as signal instances of Divine vengeance, and as sure proofs that the wicked shall not go unpunished. 2Pet 2:6, Jude 1:7

(e) "shall be more tolerable" Mt 11:22,24