The Messenger of Allah ﷺ said, "When a dog laps from the vessel of one of you, let him wash it seven times."
وقال رسول الله ﷺ إذا ولغ الكلب في إناء أحدكم فليغسله سبع مرات
Its isnad is sahih. It was previously mentioned in 7140. Shafii narrated it with this wording on p. 8, and with similar wording Muslim narrated it in 1/234 no. 280, Abu Dawud in 1/19 no. 73, and Nasai in 1/54 no. 67.