Hadith #252The Book of Purification and its Sunnah · Narrated by Hammad bin Salama حماد بن سلمة, Ibrahim bin al-Hjaj bin Zayd إبراهيم بن الحجاج بن زيد, Musa bin Isma'il al-Munqari al-Tabudhaki موسى بن إسماعيل المنقري - لتبوذكي
“The Messenger of Allah said: ‘If the water is the amount of two or three Qullah, nothing can make it impure (Najis).'” (Sahih)
Another chain with similar wording.