Bechorot 26: When to Give the Kohen his Bechor

Today's day begins our fourth perek.  When must we redeem the firstborn kosher animal?  Do we care for it for a month, like with firstborn boy children, or is there another set time?  The Mishna asks: Until when must an Israelite ten to an raise a firstborn? With regard to a small animal, thirty days.  With regard to a large animal, fifty days.  

RabbI Yosei says that a small animal waits three months; the priest cannot just demand it.  But if the priest says, "give tt to me so that I can eat it", it is permitted.  In Temple times, if the firstborn was in an unblemished state and the priest said to him "give and I will sacrifice it", it was allowed.

The Sages spend some time looking for Biblical sources for these rituals in giving bechorot to kohanim.  Rambam teaches that these gifts mimic the ways that gifts are given to a king.  The gift must be fully developed.  The owner cannot give the kohen the animal until the animal requires no further care and nurture. 

The one exception is when the kohen says that he wants the animal for slaughter if that animal has a mum, a blemish that would forbid sacrifice.  As long as the animal is old enough to be slaughter for personal use or as a sacrifice than the kohen is permitted to accept this gift.