John was at this time in prison; his circumstances, his character, and the nature of the message he was sent to deliver, led those who were peculiarly attached to him, to keep frequent fasts. Christ referred them to John's testimony of him, John 3:29. Though there is no doubt that Jesus and his disciples lived in a spare and frugal manner, it would be improper for his disciples to fast while they had the comfort of his presence. When he is with them, all is well. The presence of the sun makes day, and its absence produces night. Our Lord further reminded them of common rules of prudence. It was not usual to take a piece of rough woolen cloth, which had never been prepared, to join to an old garment, for it would not join well with the soft, old garment, but would tear it further, and the rent would be made worse. Nor would men put new wine into old leathern bottles, which were going to decay, and would be liable to burst from the fermenting of the wine; but putting the new wine into strong, new, skin bottles, both would be preserved. Great caution and prudence are necessary, that young converts may not receive gloomy and forbidding ideas of the service of our Lord; but duties are to be urged as they are able to bear them.