John Chrysostom
He shews that the interval of time shall not be great, but that the coming of Christ will be presently. By the comparison of the tree He signifies the spiritual summer and peace that the just shall enjoy after their winter, while sinners on the other hand shall have a winter after summer.
This analogy also adds credit to His foregoing discourse; for wherever He speaks of what must by all means come to pass, Christ ever brings forward parallel physical laws.
All these things therefore mean what was said of the end of Jerusalem, of the false prophets, and the false Christs, and all the rest which shall happen down to the time of Christ’s coming. That He said, This generation, He meant not of the men then living, but of the generation of the faithful; for so Scripture uses to speak of generations, not of time only, but of place, life, and conversation; as it is said, This is the generation of them that seek the Lord. (Ps. 24:6.) Herein He teaches that Jerusalem shall perish, and the greater part of the Jews be destroyed, but that no trial shall overthrow the generation of the faithful.
He brings forward the elements of the earth to shew that the Church is of more value than either heaven or earth, and that He is Maker of all things.