It was narrated from Ubayy bin 'Imarah, in whose house the Messenger of Allah performed prayer facing both prayer direction, that :
He said to the Messenger of Allah: "Can I wipe over my leather socks?" He said: "Yes." He said: "For one day?" He said: "For two days?" He said: "For three?" And so on, until the number reached seven. He (the Prophet) said: "For as long as you see fit." (DE)
English reference (DE): Vol. 1, Book 1, Hadith 557 (DE)
Arabic reference (DE): Book 1, Hadith 600 (DE)