3,190. A Forgotten Pledge

Hilchos Matnos Aniyim 8:2

If someone adds on to a vow to give charity, he is obligated the same as with other vows. For example, if he said, “This coin is like that one (which was committed to charity),” then the second coin is also committed to charity. If someone puts a coin aside and says, “This is for charity,” after which he takes another coin and says, “And this,” the second is also for charity even though he didn’t explicitly call it such.

Hilchos Matnos Aniyim 8:3

If someone makes a charity vow but he forgets the amount, he must give charity until he’s sure that he didn’t intend to give that much.