“For the law was given by Moses, but grace and truth came by Jesus Christ.”
John 1:17 KJV
“He also told them a parable: “No one tears a piece from a new garment and puts it on an old garment. If he does, he will tear the new, and the piece from the new will not match the old. And no one puts new wine into old wineskins. If he does, the new wine will burst the skins and it will bespilled, and the skins will be destroyed. But new wine must be put into fresh wineskins.”
Luke 5:36-38 ESV
“For on the one hand, a former commandment is set aside because of its weakness and uselessness (for the law made nothing perfect); but on the other hand, a better hope is introduced, through which we draw near to God.”
Hebrews 7:18-19 ESV
You don’t put new wine (unfermented wine) into old wineskins. You’d need to use new wineskins because as the fermentation process occurs only new wineskins can accommodate the expansion of the gas. New wine in old wineskins would cause the old wineskins (which are already stretched) to burst and the wine would be lost. The Old Covenant law could never stretch enough to accommodate the New Covenant truths of mercy and grace.