Abundance of disagreement among the muqallids and its rarity among the people of hadith:

Whoever grasps this underlying reason for the disgraceful, centuries-long fragmentation of the various camps of muqallids will understand how most of them came to issue fatwas declaring the prayer behind someone of another madhhab invalid—or at least reprehensible. Some even forbade a Hanafi man to marry a Shafiʿi woman, while another jurist allowed that pairing but not the reverse, justifying his ruling by saying, “We treat her as though she were one of the People of the Book.” It is as though Allah never addressed them with His words, “Do not be like those who split up and differed after clear proofs had come to them” (Q 3:105), and His words, “Yet they tore their affair into fragments; every faction rejoicing in what it possessed” (Q 23:53).

Ibn al-Qayyim, d. 751 AH, said ⦗1/314⦘: “The term zubur means ‘books’—that is, every faction authored books of its own, adopted them, acted according to them, and promoted them to the exclusion of the books of the other factions, which is exactly what we witness today.”

I say: These very books are most likely what ʿAbd Allah ibn ʿAmr, may Allah be pleased with them both, alluded to in the report transmitted from him by ʿAmr ibn Qays al-Sukuni, who said: “I traveled with my father as part of the delegation to Muʿawiyah, and I heard a man addressing the people and saying, ‘Among the portents of the Hour are that the wicked will be elevated while the righteous will be debased,¹ that deeds will be hoarded away and only words will be displayed, and that people will recite from al-Mathnāh among a group in which no one challenges or denounces it.’”