Peter Pett's Commentary on the Bible
Leviticus 22:26-30
Further Instructions In Respect Of Offerings (Leviticus 22:26).
It is noteworthy that behind all these examples the special idea of thoughtfulness and consideration stands out. God's people are not to be callous or greedy. They must do what is seemly.
‘And Yahweh spoke to Moses, saying,'
Again a word of God through Moses.
“When a bull ox, or a sheep, or a goat, is born, then it shall be seven days under the dam, and from the eighth day and from then on it shall be accepted for the oblation of an offering made by fire to Yahweh.”
No animal may be offered in sacrifice until it is at least eight days old (compare Exodus 22:30). This may be because it is seen as not yet within the covenant (as with a newborn son - Leviticus 12:3; compare also Leviticus 19:23) or it may be in order to prevent distress to the mother and not seen as fitting. Or the idea may be that until that ‘perfect period' has passed it is not really developed enough to be acceptable. All three may in fact be included, with ‘what is fitting' being especially in mind in view of what follows.
“And whether it be cow or ewe, you shall not kill it and its young both in one day.”
A mother and its young should not be slain in sacrifice on the same day. This may have been due to certain pagan practises, or may simply be on the basis of what is seemly. We can compare how a bird and its eggs should not both be taken on the same day (Deuteronomy 22:6). Having taken the eggs the bird should be allowed to go free. His people were not to be greedy or callous or thoughtless. So must they not kill a cow/ewe and its young on the same day.
“And when you sacrifice a sacrifice of thanksgiving to Yahweh, you shall sacrifice it that you may be accepted. On the same day it shall be eaten. You shall leave none of it until the morning. I am Yahweh.”
When a peace sacrifice for thanksgiving is offered it must be offered in a way that will be accepted. Especially must it all be eaten on the same day. The thanksgiving should be shared with as many as possible rather than be simply retained for the benefit of the offerer. Thus none must be left until the morning. They must remember Who Yahweh is and how generous He is, and be generous as well.