The categories of the maqlūb

The author, may Allah have mercy on him, said:

22 – Substituting any transmitter for another is one kind,
and inverting the chain for a given text is another.

His words, “Substituting any transmitter for another”…
Here the particle ma functions as an indefinite descriptive pronoun. In other words, you could replace ma with ay (“any”), so the intended sense is: “the substitution of any narrator for another.” The particle ma sometimes appears as an indefinite descriptive pronoun and sometimes as an indefinite noun being described, as in the Almighty’s statement: “Indeed, Allah—how excellent is that with which He admonishes you” (Q 4:58). An example of the first usage is the author’s phrase here: “Substituting any transmitter.”

The maqlūb is divided into two types.

The first type is the one the author just referred to with the words, “Substituting any transmitter for another,” and it is what the scholars call “reversal within the chain of transmission.” For example, a narrator might say, “Yūsuf related to me from Yaʿqūb,” but then the chain is turned around so that he says, “Yaʿqūb related to me from Yūsuf.” This inversion usually happens by mistake—through forgetfulness or the like—because there is no benefit in doing it intentionally.

Should someone ask, “How do we know that the chain has been inverted? Perhaps the way it is now stated is actually correct,” the answer is: we know it is inverted when the same report reaches us by another route that is more reliable and which contradicts the inverted version, or when the same narrator who performed the inversion once reported it correctly during his younger, more precise days, then after he grew old and his memory weakened he reported the hadith again but with the chain reversed. In such cases we judge the first rendition to be sound and the later one to be inverted.

An illustration: suppose two transmitters relate this hadith with its sound chain