Charles Spurgeon Commentary Mark 2:18-20

"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? And Jesus said unto them, Can the sons of the bridechamber fast, while the bridegroom is with them? as long as they have the bridegroom with them, they cannot fast. But the days will come, when the bridegroom shall be taken away from them, and then will they fast in that day." — Mark 2:18-20 (ASV)

While Christ was with His people in person, they could not help having joy and gladness; but when He was gone from them, they must lament His absence.