The Greek katalyō (G2647) has two related meanings: (1) to demolish, destroy, or abolish — to undo what has been built or established; (2) to unharness animals and lodge for the night. Jesus uses katalyō in two critical passages: Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them (Matthew 5:17). And at His trial: This fellow said, I am able to destroy the temple of God and rebuild it in three days (Matthew 26:61).
The two uses of katalyō in Matthew point to the same theological axis. Jesus does not come to demolish the OT scriptures but to bring them to their full intended meaning — katalyō is contrasted with plēroō (fulfill/fill up). Yet He will 'destroy' the temple in a deeper sense: His body is the true temple (John 2:19-21), and in His death and resurrection the old sacrificial system is superseded. The temple authorities feared a literal katalyō; Jesus was announcing a deeper one — the end of the Mosaic ceremonial order and the inauguration of the new covenant in His body.