It is narrated from Sa'id bin Abdullah (may Allah have mercy on him): I saw Sayyiduna Anas bin Malik (may Allah be pleased with him); he came to the toilet, then performed ablution and wiped over his white buttoned cap and over his black socks of fine cloth. (b) Some weak narrators have narrated it as marfu' (attributed to the Prophet), and that has no standing. (c) Wiping (over socks) has been narrated from Abu Umamah, Sahl bin Sa'd and Amr bin Hurayth (may Allah be pleased with them). Imam Abu Dawud (may Allah have mercy on him) said: It has also been narrated from Umar bin al-Khattab (may Allah be pleased with him) and Ibn Abbas (may Allah be pleased with them both). (d) The teacher Abu al-Walid would interpret the hadith of wiping over socks and sandals as meaning that the wiping was over socks fitted with leather (soles), not over a sock alone or a sandal alone. And I have found a report from Anas bin Malik that indicates this.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1356