A.T. Robertson Commentary Mark 14:2

"for they said, Not during the feast, lest haply there shall be a tumult of the people." — Mark 14:2 (ASV)

Not during the feast (Μη εν τη εορτη). They had first planned to kill him at the feast (John 11:57), but the Triumphal Entry and great Tuesday debate (this very morning) in the temple had made them decide to wait till after the feast was over. It was plain that Jesus had too large and powerful a following. See on Mt 26:47.