Commentaries:
Robertson's Word Pictures (NT)
Hearest thou (akoueiv). In a rage at the desecration of the temple by the shouts of the boys they try to shame Jesus, as responsible for it.
Thou hast perfected (kathrtisw). The quotation is from Psalms 8:3 (LXX text). See Matthew 4:21 where the same verb is used for mending nets. Here it is the timeless aorist middle indicative with the perfective use of kata-. It was a stinging rebuke.
Other Robertson's Word Pictures (NT) entries containing Matthew 21:16:
Mark 11:11
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