1,229. Various Scenarios in Donating the Half-Shekel
Shekalim 3:12
If a person puts a half-shekel aside because he thinks that he is obligated to give it but he subsequently discovers that he is not so obligated, the coin is not sanctified. If a person donates two half-shekels and subsequently discovers that he was only obligated to give one, then if he donated them sequentially, the second coin is not sanctified. If he donated them simultaneously, then one is his half-shekel and the other is an unsanctified surplus to his half-shekel. If someone puts aside his half-shekel and dies, it should be designated as a donation to the Temple.
Shekalim 3:13
If a person takes coins in his hand and says that they are for his half-shekel, or if he collects smaller denominations of coins and says that he is gathering them for his half-shekel, then even if he collects a whole purse full of money, all he must give is the regular obligatory half-shekel; the rest of the money is not sanctified. Any surplus payment given with the half-shekel remains unsanctified.