Is it permissible to cover the eyes of animals before slaughtering them as an act of kindness, so they do not see the knife and the slaughtered animals?

There is no religious evidence regarding the recommendation to cover the eyes of the slaughtered animal. Recommendation is a legal ruling that can only be established with evidence.

However, if covering the eyes is intended for kindness and mercy towards the animal, such as when the knife or other slaughtered animals are in front of it, or if the animal is looking at the knife and the knife cannot be hidden from it except by covering its eyes, then in this case, covering is permissible and desirable, due to the general texts on kindness during slaughter and mercy towards the slaughtered animal. Allah has ordained kindness in everything, and commanded kindness in slaughter, and providing comfort to the slaughtered animal, as stated in the Hadith of Shaddad ibn Aws: "When you slaughter, slaughter well, and let each one of you sharpen his blade and relieve his slaughtered animal." It is also forbidden to sharpen the knife in the presence of the animal, or to slaughter one in the presence of another, or to drag it to its slaughter place, as well as forbidding causing the animal multiple deaths, such as sharpening the knife while it is watching.