"Tell us by what authority you do these things, or who it is that gave you this authority" (v2). When the religious leaders interrogated Jesus, he didn’t bother discussing technicalities; instead, he asked them what they thought of John the Baptist. Jesus’ authority was obvious to those who were sincerely looking for the Messiah, just as John’s testimony was clearly from God. Jesus’ parable made it clear that in rejecting him, they were rejecting God’s “beloved son” (v13).
“The stone that the builders rejected has become the cornerstone” (v17). Jesus is “the cornerstone” of our faith. Without Him, nothing else can save us, and if we have Him, we have everything.