They differed as to the minimum amount of Qur’anic recitation that fulfils the requirement:
Some maintained that the recitation of three verses is sufficient, a view ascribed to Saʿīd ibn Jubayr.
Others said: rather, three short verses—or one long verse equal to them; this is the opinion of Abū Yūsuf and Muḥammad.
Yet others held that the recitation of a single verse, without qualification, suffices. This view is reported from Abū Ḥanīfa, and a number of our own scholars relate it as one of the narrations from Aḥmad, noting that Harb transmitted it from him. The Qāḍī said in al-Jāmiʿ al-Kabīr that he found, in the handwriting of some of our companions, [ … ] (1) and in the book of Abū Isḥāq ibn Shaqlā (2).

Abū Bakr ʿAbd al-ʿAzīz told us: al-Khallāl narrated to me, saying, ‘Harb al-Kirmānī reported: I said to Abū ʿAbd Allāh, “A man recited one verse of the Qur’an and did not recite al-Fātiḥa; is his prayer valid?” He replied, “The prayer is valid.” I said, “But the Prophet ﷺ said, ‘There is no prayer for the one who does not recite the Opening of the Book.’” He answered, “That is meant as counsel toward excellence, not as a binding obligation…”’