Numbers 3:13

3:13 because all the firstborn are mine. When I destroyed ¹  all the firstborn in the land of Egypt, I set apart for myself all the firstborn in Israel, both man and beast. They belong to me. I am the Lord.” ² 

Numbers 5:18

5:18 Then the priest will have the woman stand before the Lord, uncover the woman’s head, and put the grain offering for remembering in her hands, which is the grain offering of suspicion. The priest will hold in his hand the bitter water that brings a curse. ³ 

Numbers 29:13

29:13 You must offer a burnt offering, an offering made by fire as a pleasing aroma to the Lord: thirteen young bulls, two rams, and fourteen lambs each one year old, all of them without blemish.

[3:13]  ¹ tn The form הַכֹּתִי (hakkoti) is the Hiphil infinitive construct of the verb נָכָה (nakhah, “to strike, smite, attack”). Here, after the idiomatic “in the day of,” the form functions in an adverbial clause of time – “when I destroyed.”

[3:13]  ² sn In the Exodus event of the Passover night the principle of substitution was presented. The firstborn child was redeemed by the blood of the Lamb and so belonged to God, but then God chose the Levites to serve in the place of the firstborn. The ritual of consecrating the firstborn son to the Lord was nevertheless carried out, even with Jesus, the firstborn son of Mary (Luke 2:22-23).

[5:18]  ³ tn The expression has been challenged. The first part, “bitter water,” has been thought to mean “water of contention” (so NEB), but this is not convincing. It has some support in the versions which read “contention” and “testing,” no doubt trying to fit the passage better. N. H. Snaith (Leviticus and Numbers [NCB], 129) suggests from an Arabic word that it was designed to cause an abortion – but that would raise an entirely different question, one of who the father of a child was. And that has not been introduced here. The water was “bitter” in view of the consequences it held for her if she was proven to be guilty. That is then enforced by the wordplay with the last word, the Piel participle הַמְאָרֲרִים (ham’ararim). The bitter water, if it convicted her, would pronounce a curse on her. So she was literally holding her life in her hands.