3,259. Separating Terumah Conditionally
Terumos 4:17
Regarding one who separates terumah conditionally, if the condition is fulfilled, what he separated is terumah; if not, it’s not terumah. If someone takes terumah or maaser and then regrets doing so, he can approach a Torah scholar and request for his commitment to be overturned, the same as one can do for other vows. In such a case, the produce reverts to its previous secular status until he separates terumah again, either from the same produce or from different produce.
Terumos 4:18
Let’s say that someone draws terumah from a wine vat, declaring the contents of his vessel to be terumah on the condition that it ascends from the vat intact. In order for the contents of his vessel to be terumah, it must ascend from the vat without breaking or splitting; being rendered ritually unclean does not violate his condition. If the vessel breaks, causing the wine to fall back into the vat, it does not render the mixture meduma (a combination of tithed and untithed produce). If the vessel was successfully drawn from the vat and placed in a location where, if it breaks or rolls, it won’t reach the vat, then the condition has been met. Therefore, if the wine that was withdrawn is returned to the vat, the mixture is rendered meduma.