This which here follows is related both by Mark and Luke, without any question of discrepancy; indeed they do not say, “At that time,” so that Matthew has here perhaps preserved the order of time, they that of their recollection; unless we take the words in a wider sense, “At that time,” that is, the time in which these many and divers things were done, whence we may conceive that all these things happened after the death of John. For he is believed to have been beheaded a little after he sent his disciples to Christ. So that when he says “at that time,” he may mean only an indefinite time.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: De Cons. Ev., ii, 34