A conditional gift TB Baba Batra 137

On daf TB Baba Batra 137 the Gemara goes on a slight tangent by discussing the laws of an lulav and etrog. According to the Torah the person waving the lulav and etrog must own it and not just borrow it on the first day. “It is taught in another baraita that Rabbi Eliezer says: Just as a person does not fulfill his obligation on the first day of the Festival with the lulav of another, as it is written: “And you shall take for yourselves on the first day the fruit of a beautiful tree, branches of a date palm” (Leviticus 23:40), and the Sages derive from the phrase: Shall take for yourselves, that it must be taken from your own and not from that of someone else…” TB Sukkah 27b, Sefaria.org translation)

Ideally each Jew should own his own lulav and etrog; however, we know that is not always possible. Sometimes the cost of the lulav and etrog is prohibitive for each person to own his own and sometimes the ability to import a lulav and etrog for everyone is impossible. We have stories that there was only one lulav and etrog for an entire small European shtetel. Daf TB Baba Batra 137 teaches how we can surmount those challenges. It answers the question can one gift his lulav and etrog on the condition that that person return it to him?

“Rava says: If one person said to another: This etrog is given to you as a gift on the condition that you return it to me, and the recipient took it on Sukkot and attempted to fulfill his obligation with it, if he ultimately returned it, he has fulfilled his obligation; if he did not return it, he has not fulfilled his obligation, as he did not fulfill the condition, thereby retroactively invalidating the gift. The Gemara explains that Rava teaches us that a gift given on the condition that it be returned is considered a valid gift.” (Sefaria.org translation)

There is another occasion where a conditional gift works. Today the groom gives a ring to the bride for the purposes of kiddushin, engagement, underneath the huppah before the marriage ceremony. The groom has to own that ring for the kiddushin to be valid. Sometimes somebody in the family has an heirloom ring  and the groom wishes to use that special ring for the purposes of kiddushin. If the owner of the ring gives it to the groom as a gift so is his for that short time underneath the huppah on the condition he returns it afterwards, the groom may use give it to his bride. If they return that ring to the original owner, then the kiddushin is valid, but if they don’t well they have more trouble than they had before.