His disciples remembered that it is written, “The zeal of your house will consume me.”
Jesus’ disciples then recalled a sentence from a Psalm (69) written about 1,000 years earlier by their then King David who was a prolific song-writer. The song is one of David in severe distress and gives the reason for his awful plight: “Zeal for your house has consumed me.”
Jesus is not yet in such distress. But the disciples think that Jesus’ “zeal” for his father’s house is such that it “will”, inevitably, “consume” him to his own death. Maybe what followed confirmed their thoughts.
So the Judeans answered and said to him, “What sign do you show to us, in that you are doing these things?” Jesus answered and said to them, “Release this sanctuary-dwelling! And in three days I will raise it up.” So the Judeans said, “This sanctuary-dwelling was forty-six years being built, and will you raise it up in three days?”
Sure enough, “the Judeans" ask for a “sign” from Jesus which would, in some way, justify his (to them) abominable conduct. “Undo this sanctuary-dwelling!” This is an instruction to them: “Undo” is in the imperative tense.
Within months they would “undo” Jesus by arranging his Roman crucifixion. “And in three days I will raise it up!” Jesus rose from the dead after “three days” in the grave. The whole Temple would itself be destroyed in AD 70.
In fact that one was stating concerning the sanctuary-dwelling of his body. So when he was raised up from dead ones, his disciples remembered that he was stating this, and they believed the scripture and the word that Jesus said.