Ibn Ezra on Leviticus 27:32

תחת השבט. שבט הרועה והנה הנבחר הוא הא׳‎ והעשירי שוה כמו זה רק העשירי יגאלנו ואין כן הבכור והנה יתן הבכור והעשירי בבהמה ובזרע הארץ שהיא התבואה הבכורים והמעשר: UNDER THE ROD. The shepherd’s rod.⁹³All animals that are under the supervision of a shepherd (Filwarg). Now the number one⁹⁴The first-born. is the chosen one. The tenth is the same as the first.⁹⁵It too is holy. However, he may redeem the tenth.⁹⁶The tithe (v. 31) referenced is probably the second tithe (Weiser). See also Rashi and the Rashbam. The reference cannot be to the tenth of the cattle and flock, for Scripture says that these cannot be redeemed (v. 33). This is not the case with the first-born.⁹⁷See Num. 18:17. Note, the Israelite shall give the first-born and the tenth of the beast, and of the seed of the ground, namely, of the produce, the first fruits⁹⁸All these are given to the kohen. and the tithe.⁹⁹The tithe is given to the Levite. The Levite then gives a tithe from the tithe given him to the kohen.