It is permissible with a dislike of a non-binding nature, meaning that if one fasts it alone, they have opposed what is preferable but do not sin; because it resembles the Jews, as mentioned in Al-Bahr Al-Ra'iq 2: 278, and Majma' Al-Anhar 1: 254. It was narrated by Abdullah bin Busr from his sister, who was deaf, that the Messenger of Allah (peace be upon him) said: "Do not fast on Saturday except for what is obligatory upon you, and if one of you finds only a grapevine twig or the bark of a tree, let him chew it," in Sahih Ibn Khuzaymah 3: 317, and Al-Mustadrak 1: 601. He said: This is a sound hadith according to the conditions of Al-Bukhari, and they did not narrate it. There is an opposing narration with a sound chain that they both narrated from Humam from Qatadah from Abu Ayyub Al-Ataki from Juwayriyyah bint Al-Harith that the Prophet (peace be upon him) entered upon her on Friday while she was fasting, and he said: "Did you fast yesterday?" She said: "No." He said: "Do you intend to fast tomorrow?"... the hadith. The hadith of the deaf woman has been discussed by the scholars, Ibn Shihab rejected it, Malik denied it, and Abu Dawood and Al-Hakim mentioned it in their versions. It was reported from Umm Salamah (may Allah be pleased with her) that she said: "The most that the Prophet (peace be upon him) used to fast was on Saturdays and Sundays, and he would say: 'They are two holidays for the polytheists, and I want to oppose them,'" in Sahih Ibn Hibban 8: 381, 407, Sahih Ibn Khuzaymah 3: 318, Al-Mustadrak 1: 602, and Sunan Al-Bayhaqi Al-Kabir 4: 303. And from Ibn Abbas (may Allah be pleased with both of them), he sent to Umm Salamah and Aisha asking them what the Messenger of Allah (peace be upon him) preferred to fast from the days, and they said: "The Messenger of Allah (peace be upon him) did not die until most of his fasting was on Saturday and Sunday, and he would say: 'They are holidays for the People of the Book, and we like to oppose them,'" in Sunan Al-Nasa'i 2: 146. Accordingly, we say it is a non-binding dislike, not a prohibition, due to the conflict in the evidence. See: The Epistle of the One Who is Unfortunate and Prohibited from Fasting on Saturday.