This verse is very similar to verse 13 (see the comments there). Certain points are repeated here for emphasis. The repeated elements must be conveyed in a corresponding manner in translation, while the variations should be expressed, where possible and natural in the target language.

But the man who is unclean and does not cleanse himself, that person shall be cut off from the midst of the assembly: But renders well the Hebrew waw conjunction (literally “And”), since it introduces a contrast here. For that person shall be cut off from the midst of the assembly, see 9.13. The Hebrew word for assembly is qahal (see 10.7).

Since he has defiled the sanctuary of the LORD: For the Hebrew verb rendered defiled, see 5.3; for the Hebrew word rendered sanctuary (miqdash), see 18.1.

Because the water for impurity has not been thrown upon him, he is unclean: For the water for impurity, see verse 9. For the Hebrew verb rendered thrown, see the comments on 18.17, where it is translated “sprinkle.” This Hebrew verb (also in verse 13) differs from the one translated “sprinkle” in verses 18-19 and 21, but the intended sense appears to be the same, perhaps with somewhat greater emphasis here.

Quoted with permission from de Regt, Lénart J. and Wendland, Ernst R. A Handbook on Numbers. (UBS Helps for Translators). Miami: UBS, 2016. For this and other handbooks for translators see here .