Or HaChaim on Deuteronomy 17:1/אור החיים על דברים י״ז:א׳

1 לא תזבח….אשר יהיה בו מום, "Do not slaughter for G'd anything blemished." The wording אשר יהיה בו מום "on which there will be a blemish," must be understood in conjunction with Sifri that our verse forbids an animal suffering from a temporary blemish. This ruling is hinted at by the word יהיה, "will be." That word includes not only permanent blemishes but even temporary blemishes. Perhaps one may also say that if the animal in question has a limb which would result in it becoming blemished unless said limb was amputated, the animal in question is considered blemished even before the operation (regardless of whether the animal is being considered for a sacrifice). The words לא תזבח …אשר יהיה בו מום mean "you must not sacrifice it…as it is going to develop a blemish" (which would disqualify it.)