Mark 2:20

“But the days will come when the Bridegroom will be taken away from them, and then they will fast in that day.”

These words confirm that we are to see in the picture of the Bridegroom something significant concerning Jesus. For the Bridegroom Who was now here, would one day be snatched away (the verb is forceful - compare Isaiah 53:8) and then they will have good cause to fast. Jesus knew already from the voice at His baptism that He was called on to fulfil the ministry of the suffering Servant, and this was confirmed by John's words, “Behold the Lamb of God, Who takes away the sin of the world” (John 1:29). Thus we have here the first indication of His awareness of the brutal end that awaited Him. He knew that He must face suffering on behalf of His people. And then indeed His disciples would fast.

Interestingly the words do not encourage regular fasting. The disciples would indeed sorrow but their sorrow would be turned into joy (John 16:20). Thus the need for fasting would quickly pass and would be no more. There is no real encouragement to fasting here.