Ibn Ezra on Leviticus 22:18

ואחרי שהזכיר קדשי בני ישראל הזהיר שלא יביאו הקדשים מבעלי המומין: After mentioning the holy things of the children of Israel²⁶The offerings of the children of Israel. See verse 2. Scripture goes on²⁷In the next section. to caution the Israelites to not bring the holy things from blemished animals.

וטעם ומן הגר. כי משפט אחד לנודר ולמתנדב לישראל ולגר כי כן כתוב וחכמים הפרישו בין נדר ובין נדבה וכל נדר נדבה ואין כל נדבה נדר וכל קרבן שיעלה כלו על המזבח ראוי להיותו בלא מום:: [STRANGERS.] Scripture reads or of the strangers for it is stated that there is one law for the Israelite and the stranger who offer a vow or freewill offering.²⁸See Num. 15:14-16. The sages differentiated between a vow offering and a freewill offering.²⁹See Kinnim 1:1. All vow offerings are freewill offerings. However, not all freewill offerings are vow offerings.³⁰One can set aside a freewill offering without taking a vow to bring a freewill offering. It is fitting that all sacrifices that are offered in their entirety³¹A burnt offering. on the altar be unblemished.³²The same applies to other offerings. I.E. speaks of a burnt offering because our verse does.