Deuteronomy 15:23

Only thou shalt not eat the blood thereof,.... Of the firstling:

thou shalt pour it upon the ground as water; See Gill on Deu 12:16; see Gill on Deu 12:23; see Gill on Deu 12:24.

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Compare Exo 13:11 ff. The directions of the preceding legislation (see Num 18:15 ff) are here assumed, with the injunction added, that the animals thus set apart to God Deu 15:19 were not to be used…

Here is, 1. A repetition of the law concerning the firstlings of their cattle, that, if they were males, they were to be sanctified to the Lord (Deu 15:19), in remembrance of, and in thankfulness for,…