(a) It is reported from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that he did not set a time limit for wiping over leather socks. (b) We have narrated from Sayyiduna Umar (may Allah be pleased with him), Sayyiduna Ali (may Allah be pleased with him), Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) and Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that a time limit for wiping is established from them, and their view agrees with the well-known Sunnah that is narrated abundantly. (c) Fundamentally, washing the feet is obligatory, and this is what is preferable. And Allah knows best. (d) Abu Ali al-Za'farani said: Imam al-Shafi'i (may Allah have mercy on him) went back to the fixed time limit for wiping when he was with us in Baghdad.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1335