Jesus was rejected in Jerusalem as the Messiah (Matthew 21 to 23). Jesus lamented this with sadness as well as with a threat of judgment (Matthew 23:37-39). But as he walked away, his disciples called attention to the temple buildings. Like most Jews, the disciples honored the temple. However, Jesus told them of what happen. The temple and all its buildings will be thrown down. His disciples wanted to know when will it happen and would that be the time when Jesus will be finalized recognized or revealed as the Messiah of Israel (i.e., the sign of your coming), thus signaling the end of the age, as they understood it. This is similar to the question attributed to them in Acts 1:6 (“Lord, are you at this time going to restore the kingdom to Israel?”). But instead of answering them directly, Jesus warned them, "Watch out that no one deceives you." Terrible things will happen before the end comes. But on the positive side, the gospel of the kingdom will be preached in the whole world, and then the end will come.