Sunan Abi Dawud 762
سنن أبي داود#762SahihShu’aib b. Abi Hamzah said:Ibn al-Munkadir, Ibn Abi Farwah and a number of jurists of Madina said to me: When you recite the supplication “I am first of the Muslims,” say instead; “I am one of the Muslims”
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih Maqtu
Muhammad Muhyi Al-Din Abdul HamidSahih Maqtu
Zubair Ali ZaiIsnaad Sahih
In-book reference: 2:372