Sahih al-Bukhari 174
Sahih al-Bukhari · Book 4: Ablutions (Wudu') · If a dog drinks from the utensil of any one of you then it is essential to wash it seven times
And narrated Hamza bin 'Abdullah:
وَقَالَ أَحْمَدُ بْنُ شَبِيبٍ حَدَّثَنَا أَبِي ، عَنْ يُونُسَ ، عَنِ ابْنِ شِهَابٍ ، قَالَ حَدَّثَنِي حَمْزَةُ بْنُ عَبْدِ اللَّهِ ، عَنْ أَبِيهِ ، قَالَ كَانَتِ الْكِلاَبُ تَبُولُ وَتُقْبِلُ وَتُدْبِرُ فِي الْمَسْجِدِ فِي زَمَانِ رَسُولِ اللَّهِ صلى الله عليه وسلم فَلَمْ يَكُونُوا يَرُشُّونَ شَيْئًا مِنْ ذَلِكَ .
My father said. "During the lifetime of Allah's Apostle, the dogs used to urinate, and pass through the mosques (come and go), nevertheless they never used to sprinkle water on it (urine of the dog.)"