Revised Standard Version renders the Hebrew text of this verse literally, which will probably be very unnatural in other languages. Good News Translation gives a good model for restructuring it.

And it shall be to you a tassel to look upon and remember all the commandments of the LORD, to do them …: The tassels will remind the Israelites of their obligation to keep the commandments of God’s Law. The Hebrew pronouns for you and your are plural, referring to the Israelites. In contrast to verse 38, in verses 39-41 the LORD addresses them directly. For commandments see verse 22. Since the LORD is speaking here, some languages may prefer to render all the commandments of the LORD as “all my commands” (Good News Translation). Do them may be rendered “obey them” (Good News Translation) or “observe them” (New Jewish Publication Society’s Tanakh). A helpful model for the first half of this verse is “When you see the tassels, you will remember and obey all my commands” (similarly New Living Translation).

Not to follow after your own heart and your own eyes: Good News Translation removes the figurative language here by rendering your own heart and your own eyes as “your own wishes and desires.” In some languages, however, either one or both of these figures may express the intended meaning naturally.

Which you are inclined to go after wantonly: The Hebrew verb rendered inclined to go … wantonly (zanah) comes from the same root as noun translated “faithlessness” in 14.33 (see the comments there). It usually refers to sexual immorality and describes the actions of a prostitute. Here the idea of prostitution and the unfaithfulness of a spouse is used to describe the way Israelites sinned against God. They were unfaithful to God like an adulterous spouse. Good News Translation renders this clause clearly, saying “turn away from me.” De Nieuwe Bijbelvertaling provides the following helpful model for the last half of this verse: “and do not become unfaithful to me by following the desires of your heart and eyes.”

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 .