Numbers 8:21

And the Levites were purified, and they washed their clothes; and Aaron offered them as an offering before the Lord; and Aaron made an atonement for them to cleanse them.

Cross-reference

Numbers 8:7 prescribes the purification ritual for Levites — this verse shows its execution: they purified themselves and washed clothes.

Numbers 8:11-13 commands the wave offering and sacrifices for Levites — this verse reports Aaron performing exactly that: wave offering and atonement.

Numbers 8:12 specifies the sin and burnt offerings for atonement — this verse mentions Aaron making atonement, referencing the sacrificial procedure.

Numbers 8:15 says after cleansing and wave offering, Levites go into service — this verse records the cleansing and offering, setting the stage for that service.

Numbers 8:13 commands to present the Levites as a wave offering, which Numbers 8:21 then fulfills in the narrative.