Imam al-Shafi'i (may Allah have mercy on him) said: The hadith of Ibn Abbas (may Allah be pleased with them both) is established from the Messenger of Allah (peace and blessings be upon him). None of the people of knowledge would reject a hadith like it even if there were nothing else on the matter besides it; moreover, there is other evidence along with it that supports it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 20637