Muwatta Imam Malik Book of Purity, Hadith 13

Yahya related to me from Malik from Ishaq ibn Abdullah ibn Abi Talha from Humayda bint Abi Ubayda ibn Farwa that her maternal aunt Kabsha bint Kab ibn Malik, who was the wife of the son of Abu Qatada al-Ansari, told her that once Abu Qatada was visiting her and she poured out some water for him to do wudu with. Just then a cat came to drink from it, so he tilted the vessel towards it to let it drink. Kabsha continued, "He saw me looking at him and said, 'Are you surprised, daughter of my brother?' I said, 'Yes.' He replied that the Messenger of Allah ﷺ said, cats are not impure. They intermingle with you .' "
Yahya said that Malik said, "There is no harm in that unless one sees impurities on the cat's mouth."

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ إِسْحَاقَ بْنِ عَبْدِ اللَّهِ بْنِ أَبِي طَلْحَةَ، عَنْ حُمَيْدَةَ بِنْتِ أَبِي عُبَيْدَةَ بْنِ فَرْوَةَ، عَنْ خَالَتِهَا، كَبْشَةَ بِنْتِ كَعْبِ بْنِ مَالِكٍ - وَكَانَتْ تَحْتَ ابْنِ أَبِي قَتَادَةَ الأَنْصَارِيِّ - أَنَّهَا أَخْبَرَتْهَا أَنَّ أَبَا قَتَادَةَ دَخَلَ عَلَيْهَا فَسَكَبَتْ لَهُ وَضُوءًا فَجَاءَتْ هِرَّةٌ لِتَشْرَبَ مِنْهُ فَأَصْغَى لَهَا الإِنَاءَ حَتَّى شَرِبَتْ قَالَتْ كَبْشَةُ فَرَآنِي أَنْظُرُ إِلَيْهِ فَقَالَ أَتَعْجَبِينَ يَا ابْنَةَ أَخِي قَالَتْ فَقُلْتُ نَعَمْ . فَقَالَ إِنَّ رَسُولَ اللَّهِ ﷺ قَالَ " إِنَّهَا لَيْسَتْ بِنَجَسٍ إِنَّمَا هِيَ مِنَ الطَّوَّافِينَ عَلَيْكُمْ أَوِ الطَّوَّافَاتِ " .