Muwatta Malik 501
موطأ مالك#501SahihYahya related to me from Malik from Ziyad ibn Abi Ziyad from Talha ibn Ubaydullah ibn Kariz that the Messenger of Allah, may Allah bless him and grant him peace, said, "The best dua is dua on the day of Arafa, and the best thing that I or the Prophets before me have said is 'There is no god but Allah, alone, without any partner' (La ilaha illa'llah, wahdahu la sharika lah)
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Salim al-HilaliSahih Lighairihi
In-book reference: 15:32