Neither do men put new wine into old wineskins: else the wineskins break, and the wine runs out, and the wineskins perish: but they put new wine into new wineskins, and both are preserved.
All Commentaries on Matthew 9:17 Go To Matthew 9
George Leo Haydock
New wine into old bottles. These vessels were made of skins, or were leather bottles, in which wine used to be carried and kept. (Witham)
They were made of goat-skins prepared and sewed together, as is common in Spain and other southern countries to this day. (Haydock)
They were to wait till they were renewed by the Holy Spirit, before they could enter with advantage on the hard ways of penance. (Bible de Vence)