Luke 5:37

5:37 And no one pours new wine into old wineskins. If he does, the new wine will burst the skins and will be spilled, and the skins will be destroyed.

sn Wineskins were bags made of skin or leather, used for storing wine in NT times. As the new wine fermented and expanded, it would stretch the new wineskins. Putting new (unfermented) wine in old wineskins, which had already been stretched, would result in the bursting of the wineskins.