TSK · Numbers 18:17

And he shall lay his hand upon the head of his oblation, and kill it at the door of the tent of meeting: and Aaron's sons the priests shall sprinkle the blood upon the altar round about.

All the firstling males that are born of thy herd and of thy flock thou shalt sanctify unto Jehovah thy God: thou shalt do no work with the firstling of thy herd, nor shear the firstling of thy flock.