It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him): When a cat puts its mouth into a vessel, it is to be washed seven times.
But Ibn Jurayj and others narrated it from Ata as his own saying.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1173