(Bamidbar 5:10) "And every man, his holy things, to him shall they be": What is the intent of this? Because it is written (Ibid. 18:19) "All the terumoth of the holy things which the children of Israel will separate for the L-rd have I given to you (Aaron) and to your sons, etc.", I might think that he (a Cohein) could forcibly seize them (the priestly gifts). It is, therefore, written "And every man, his holy things, to him shall they be" — He has the option of giving them to any Cohein he wishes.
"And a man, his holy things, to him shall they be": If one measured out (terumah) for them (certain Cohanim) on the ground and others (later) joined them, I might think that I pronounce over him "Whatever a man gives to the Cohein, (in this instance the Cohein for whom he measured it out), to him (that Cohein) shall it be"; it is, therefore, written "And every man, his holy things, to him (the man) shall they be" (i.e., he retains the option of giving it to those who came later).
I might then think that if he measured it out (for him) in a basket and others joined later, I still pronounce over him "And every man, his holy things, to him (the man) shall they be" (and he can give it to the later ones); it is, therefore, (for such a circumstance) written "Whatever a man gives to the Cohein, (in this instance, the first Cohein), to him (that Cohein) shall it be." R. Yossi says if one redeemed his (first-born) son within thirty days, and he (the son) died, I might think that I pronounce over him (the father) "Whatever a man gives to the Cohein to him (the Cohein) shall it be"; it is, therefore, written "And every man, his holy things, to him (the man) shall they be." (If he died) after thirty days, the money is not taken back from the Cohein, it being pronounced over the father "Whatever a man gives to the Cohein, to him (the Cohein) shall it be."