"I asked Safwan bin 'Assal about wiping over the Khuffs, and he said: 'The Messenger of Allah ﷺ used to tell us, when we were travelling, to wipe over our Khuffs and not take them off for three nights in the event of defecating, urinating or sleeping; only in the case of Janabah.'" (Using translation from Nasāʾī 127)  

«كَانَ رَسُولُ اللهِ ﷺ» يَأْمُرُنَا إِذَا كُنَّا مُسَافِرِينَ أَنْ نَمْسَحَ عَلَى خِفَافِنَا وَلَا نَنْزِعُهَا ثَلَاثَةَ أَيَّامٍ مِنْ غَائِطٍ وَبَوْلٍ وَنَوْمٍ إِلَّا مِنْ جَنَابَةٍ اللَّفْظُ لِأَحْمَدَ  

"I came to a man called Safwan bin 'Assal and sat at his door. He came out and said: 'What do you want?' I said: 'I am seeking knowledge.' He said: 'The angels lower their wings for the seeker of knowledge out of pleasure at what he is seeking.' He said: 'What do you want to know about?' I said: 'About the Khuffs.' He said: 'When we were with the Messenger of Allah ﷺ on a journey, he told us not to take them off for three days except in the case of Janabah, but not in the case of defecation, urinating or sleep.'" (Using translation from Nasāʾī 158)  

إِنَّ الْمَلَائِكَةَ تَضَعُ أَجْنِحَتَهَا لِطَالِبِ الْعِلْمِ رِضًى بِمَا يَطْلُبُ قَالَ عَنْ أَيِّ شَيْءٍ تَسْأَلُ؟ قُلْتُ عَنِ الْخُفَّيْنِ قَالَ كُنَّا إِذَا كُنَّا مَعَ رَسُولِ اللهِ ﷺ فِي سَفَرٍ «أَمَرَنَا أَنْ لَا نَنْزِعَهُ ثَلَاثًا إِلَّا مِنْ جَنَابَةٍ وَلَكِنْ مِنْ غَائِطٍ وَبَوْلٍ وَنَوْمٍ»