We have already learned that a person cannot decide who receives portions of his estate after he dies – that will be determined by Torah law – but he can make any decisions that he wants about dividing up his property during his lifetime. The Mishna on today’s daf describes a person who writes to his sons that he is giving them his property “from today and after my death.” What he accomplishes with this is that the property will transfer at that time according to his wishes, but until that time, he will be able to use the property.
The Gemara questions this ruling, pointing out that with regard to gittin – divorce law – a get that says “from today and after my death” will be viewed as a questionable get. In response, the Gemara distinguishes between divorce law where it is not clear to us whether the clause “after my death” is a condition that will activate the divorce from the earlier date or if it is a negation of the planned divorce from today. In our case, however, both statements can be meaningful – ownership of the land will transfer at the time of death, even as it remains in the possession of the original owner until that time.
The Rashbam explains that a person might make such a present during his lifetime if he is about to enter into a second marriage, and he does not want his children from the first marriage to lose part of their estate because of obligations that he has to his new wife. Were he to simply write that they would get the money after his death, it would have no validity, since he cannot choose how to divide his possessions after he has died. This method allows him to continue using the land having ensured that it would be divided according to his wishes at the time of his death.