'Firstlings' in the Bible

you shall set apart and dedicate to the Lord all that first opens the womb. All the firstborn males of your livestock shall be the Lord’s.

You shall take the Levites for Me instead of and as a substitute for all the firstborn among the Israelites. I am the Lord; and you shall take the cattle of the Levites instead of and as a substitute for all the firstborn among the cattle of the Israelites.”

There you shall bring your burnt offerings, your sacrifices, your tithes, the contribution of your hand, your votive (pledged, vowed) offerings, your freewill (voluntary) offerings, and the firstborn of your herd and of your flock.

You are forbidden to eat within your [city] gates the tithe of your grain or new wine or oil, or the firstborn of your herd or flock, or any of your votive offerings, or your freewill offerings, or the contribution of your hand.

You shall eat the tithe (tenth) of your grain, your new wine, your oil, and the firstborn of your herd and your flock before the Lord your God in the place where He chooses to establish His Name (Presence), so that you may learn to fear [and worship] the Lord your God [with awe-filled reverence and profound respect] always.

as well as the firstborn of our sons and of our cattle, as is written in the Law, and the firstborn of our herds and flocks, to bring to the house of our God, for the priests who minister in the house of our God.