1. Rosin attests to two different texts that he found here: “ותיטיב לך ולו” or “ותטיב לו.” I prefer the second and have translated in that way above.
Traditionally, verses 23-26 have been understood as a reference to the “second tithe,” the tithe that Israelites separate from the produce of their fields not in order to give to some worthy recipient, but in order to take to Jerusalem and consume there. At the end of the section outlining that duty, the verse says that the Israelites are not supposed to neglect the Levites, even though second tithe duties have nothing to do with Levites. Rashi interprets our verse to mean: “As you were just now commanded to observe the rules of the second tithe, so you must also remember the first tithe, the one that is given to the Levite.” (So also Ibn Ezra.) Sifre 108 says that the verse teaches that Israelites have to take care of Levites in whatever way is appropriate. (So also Hizq.) Rashbam offers a contextual explanation. Mention of the Levites is relevant in a text about second tithes, since Israelites are requested to share their bounty with others, including Levites, when they eat their second tithe food in Jerusalem. In that way, our verse reiterates the theme of Deuteronomy 12:12. See similarly NJPSC.