Hadith 341
امسح على الخفين قال نعم قال يوما و يومين حتي بلغ سبعا قال له ما بدالك
"(Ibn Abi Amarah, may Allah be pleased with him, asked, O Messenger of Allah!) Should I wipe over the socks? The Prophet (peace and blessings be upon him) said: Yes. He said: For one or two days, until he mentioned seven days; so the Prophet said: For as long as you find it suitable."