Sayyiduna Safwan bin Assal (may Allah be pleased with him) says: "The Messenger of Allah (peace and blessings be upon him) granted us a concession in wiping, for the traveller up to three days, except from major ritual impurity (janabah), (for which they are to be removed); but they are not to be removed for relieving oneself, urine or passing wind."
(b) Abu al-Walid says that no one other than Mis'ar narrated the words 'or wind'.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 558