It is narrated from Imam Mujahid (may Allah have mercy on him) that Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: "When the water amounts to two large jars (qullahs) or more, nothing makes it impure."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1247