Expositor's Bible Commentary Commentary Mark 2:18

"And John`s disciples and the Pharisees were fasting: and they come and say unto him, Why do John`s disciples and the disciples of the Pharisees fast, but thy disciples fast not?" — Mark 2:18 (ASV)

In the law the only required fast was on the Day of Atonement (Leviticus 16:29, 31; 23:27–32), but after the Exile four other annual fasts were observed by Jews (Zechariah 7:5; Zechariah 8:19). In NT times the stricter Pharisees fasted twice a week (Monday and Thursday; cf. Lk 18:12). The phrase “the disciples of the Pharisees” (used only here in the NT) probably refers to people who were influenced by the teachings and practice of the Pharisees. Both they and John the Baptist’s disciples were fasting.

Why they were doing this, Mark does not say, but their fasting was a sign of true piety. Therefore, some unidentified people asked why Jesus’ disciples did not give evidence of true religious piety by fasting.