It is disliked without a valid excuse to leave the recommended sitting; for Ibn Mas'ud, may Allah be pleased with him, said: "It is better for me to sit on two stones than to sit in prayer cross-legged," in the Musannaf of Abdul Razzaq 2: 196. As for the hadith of Aisha, may Allah be pleased with her: "I saw the Messenger of Allah, peace be upon him, praying cross-legged," in Sahih Ibn Khuzaymah 2: 89, and Sahih Ibn Hibban 6: 257, it is understood to refer to a situation of necessity. See: Al-Durr Al-Mukhtar 1: 433.