At this time - Rather, "The counsel which Ahithophel has given this time is not good." He contrasts it with that given before 2-Samuel 16:21, which was good. This gave an appearance of candour to his conduct, and so gave weight to his dissent. Observe the working of David's prayer 2-Samuel 15:31.

And Hushai said unto Absalom, The counsel that Ahithophel hath given [is] not (c) good at this time.
(c) Hushai shows himself faithful to David, in that he reproves this wicked counsel and purpose.

And Hushai said to Absalom,.... Having leave to give his opinion freely:
the counsel that Ahithophel hath given is not good at this time; he owns that Ahithophel was a good counsellor, and that the counsel he gave was for the most part, if not always, good, but what he gave at this time was not so; the wisest of men may sometimes be mistaken. Abarbinel thinks he respects his former counsel, particularly that that was good, advising him to defile his father's bed, 2-Samuel 16:21; but this was not, for which he gives the following reasons.