Matthew 9:14-17
King James Version (KJV)
14Then came to him the disciples of John, saying, Why do we and the Pharisees fast oft, but thy disciples fast not?
15And Jesus said unto them, Can the children of the bridechamber mourn, as long as the bridegroom is with them? but the days will come, when the bridegroom shall be taken from them, and then shall they fast.
16No man putteth a piece of new cloth unto an old garment, for that which is put in to fill it up taketh from the garment, and the rent is made worse. 17Neither do men put new wine into old bottles: else the bottles break, and the wine runneth out, and the bottles perish: but they put new wine into new bottles, and both are preserved.
The mourning and the fast that Jesus spake of to come upon the children of the bridechamber was not a literal fast but a spiritual fast. The Lord prophesied in the prophets that the days of famine would come upon the land, but not a famine of food or drink, but of hearing the Word of the Lord.
This period of darkness would happen when the Bridegroom(Jesus) would be taken from the world. Just as Jesus said I am the Light of the world, walk while you have the Light. But Jesus also said the days would come when the Light would leave the world and darkness would soon follow, and no man would be able to work.
The parable of the old garment and new, and the old vessel and new wine and new vessel have to with the old nature in man(fleshy minded) and the new nature in man(spiritually minded) after recieving the Holy Spirit.
The old man nature(vessel) was under the law of sin unto death, but the new man nature(vessel) is born a new man in Christ. These are also shown in both the old and new covenants. Just as we are made a new creature in Christ(new vessel) so that we are able to recieve, and hold fast to the new wine(new covenant) which was given to us by way of the Body and blood of Christ.
Just as Jesus said when he took the bread, take eat, this is my Body, and Jesus also said when he took the wine, this is my blood of the new testament, which is shed for many for the remission of sins.
But the old man cannot recieve the new wine until he is made a new vessel in Christ, just as many of the Jews of that day said the old wine is better, and desired not the new.