Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
tirmidhi:2720Muḥammad b. Bashhār And Naṣr b. ʿAlī > Abū Aḥmad > Sufyān > al-Ḍaḥḥāk b. ʿUthmān > Nāfiʿ > Ibn ʿUmar

that a man gave the Salam to the Prophet ﷺ while he was urinating, but the Prophet ﷺ did not return the Salam to him."  

Abū ʿĪsá said that this Ḥadīth is Ḥasan-Ṣaḥīḥ.
الترمذي:٢٧٢٠حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ وَنَصْرُ بْنُ عَلِيٍّ قَالاَ حَدَّثَنَا أَبُو أَحْمَدَ عَنْ سُفْيَانَ عَنِ الضَّحَّاكِ بْنِ عُثْمَانَ عَنْ نَافِعٍ عَنِ ابْنِ عُمَرَ

أَنَّ رَجُلاً سَلَّمَ عَلَى النَّبِيِّ ﷺ وَهُوَ يَبُولُ فَلَمْ يَرُدَّ عَلَيْهِ يَعْنِي السَّلاَمَ حَدَّثَنَا مُحَمَّدُ بْنُ يَحْيَى النَّيْسَابُورِيُّ حَدَّثَنَا مُحَمَّدُ بْنُ يُوسُفَ عَنْ سُفْيَانَ عَنِ الضَّحَّاكِ بْنِ عُثْمَانَ بِهَذَا الإِسْنَادِ نَحْوَهُ وَفِي الْبَابِ عَنْ عَلْقَمَةَ بْنِ الْفَغْوَاءِ وَجَابِرٍ وَالْبَرَاءِ وَالْمُهَاجِرِ بْنِ قُنْفُذٍ  

قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ