Some had been speaking of how the temple was adorned, and Jesus said it would be thrown down. They asked two things. The first presses for a time: when will this happen? The second presses for a warning: what sign will show it is about to happen? Gill says "these things" means the temple's destruction, when "one stone shall not be left upon another." Matthew Henry observes, "It is natural to us to covet to know future things and the time of them," though it is more important to ask how to prepare for them.

Jesus began with a warning before a timetable: "Take heed that ye be not deceived" (Luke 21:8). He told them not to be terrified by wars, "for these things must first come to pass; but the end is not by and by" (Luke 21:9). He answered the question of the sign directly: "when ye shall see Jerusalem compassed with armies, then know that the desolation thereof is nigh" (Luke 21:20). He ended not with a date but with a call: "Watch ye therefore, and pray always" (Luke 21:36).

The temple in Jerusalem was the center of Jewish worship. Barnes describes the "goodly stones" as "Beautiful stones," either the large, finished stones of its walls or precious stones used in decorating it. The "gifts" were offerings given to adorn the temple (ESV: "noble stones and offerings," Luke 21:5).

Luke does not name the place of the question; the talk follows Jesus watching gifts cast into the temple treasury (Luke 21:1-5). Matthew and Mark say it was asked on the Mount of Olives, across from the temple (Matthew 24:3; Mark 13:3). Barnes says the account of the destruction of Jerusalem in Luke 21 is "fully considered" in his notes on Matthew 24, where he writes that it "took place about forty years after this was spoken."

Jesus had already wept over Jerusalem and said its enemies would "not leave in thee one stone upon another" (Luke 19:41-44). Now His followers ask when. His answer shows a God who warns His people ahead of time so they will not be caught off guard or led astray (Luke 21:8, 34-36).

Jesus gives them what they need, not everything they want. He names signs, but He spends most of His answer on how to live: do not be deceived, do not be terrified, be patient, watch and pray (Luke 21:8-9, 19, 36). Matthew Henry notes that those most curious about the things of God are also "in most danger of being imposed upon" and so most need to be on guard. Jesus answers their curiosity by shaping their faithfulness.