These verses seem to point at Christ's second coming, to judge the world; the disciples, in their question, had confounded the destruction of Jerusalem and the end of the world (Mat 24:3), which was built upon a mistake, as if the temple must needs stand as long as the world stands; this mistake Christ rectifies, and shows that the end of the world in those days, those other days you enquire about, the day of Christ's coming, and the day of judgment, shall be after that tribulation, and not coincident with it. Let those who live to see the Jewish nation destroyed, take heed of thinking that, because the Son of man doth not visibly come in the clouds then, he will never so come; no, he will come after that. And here he foretels,
1. The final dissolution of the present frame and fabric of the world; even of that part of it which seems least liable to change, the upper part, the pure and more refined part; The sun shall be darkened, and the moon shall no more give her light; for they shall be quite outshone by the glory of the Son of man, Isa 24:23. The stars of heaven, that from the beginning had kept their place and regular motion, shall fall as leaves in autumn; and the powers that are in heaven, the heavenly bodies, the fixed stars, shall be shaken.
2. The visible appearance of the Lord Jesus, to whom the judgment of that day shall be committed (Mar 13:26); Then shall they see the Son of man coming in the clouds. Probably he will come over that very place where he sat when he said this; for the clouds are in the lower region of the air. He shall come with great power and glory, such as will be suited to the errand on which he comes. Every eye shall then see him.
3. The gathering together of all the elect to him (Mar 13:27); He shall send his angels, and gather together his elect to him, to meet him in the air, Th1 4:17. They shall be fetched from one end of the world to the other, so that none shall be missing from that general assembly; they shall be fetched from the uttermost part of the earth, most remote from the places where Christ's tribunal shall be set, and shall be brought to the uttermost part of heaven; so sure, so swift, so easy, shall their conveyance be, that there shall none of them miscarry, though they were to be brought from the uttermost part of the earth one way, to the uttermost part of the heaven another way. A faithful Israelite shall be carried safely, though it were from the utmost border of the land of bondage to the utmost border of the land of promise.

Had shortened those days - Because of his chosen, added by D, Armenian, and five of the Itala. See Mat 24:22.

And then he shall send his angels,.... The ministers of the Gospel to preach it, and plant more churches among the Gentiles, since that at Jerusalem was entirely broken up:

and shall gather together his elect; that is, he the son of man, or Christ, shall gather them by the ministry of his servants; or "they shall gather them", as the Ethiopic version reads; and as Beza says it is read in a certain copy: these ministers shall be the means of gathering such whom God has chosen from all eternity, to obtain salvation by Christ, out of the world, and unto Christ, and into a Gospel church state: even

from the uttermost part of the earth, to the uttermost part of the heaven; be they where they will, on earth, and under the whole heavens; See Gill on Mat 24:31.