And he—may Allah have mercy upon him—said:

27 – When every peer transmits from his fellow,
It is mudabbaj; so know it well and cherish it.

This is the twenty-seventh category of ḥadīth mentioned in the poem, namely the mudabbaj.

He defined it with the words: “When every peer transmits…,” and so on.

A qarīn (peer) is a companion of the one from whom he narrates, someone who matches him either in age or in study under the same shaykh.

Thus, when it is said, “So-and-so is a peer of so-and-so,” it means they share either age or attendance upon the same teacher—such as both having studied with him in the same year, and the like.

When peers narrate from one another, ḥadīth scholars call this riwāyat al-aqrān, “the narration of peers.” Hence the biographical works state: “His narration from so-and-so is of the narration of peers,” that is, they are equal either in age or in taking knowledge from the same shaykh. If each of them, in turn, narrates from the other, the report is called mudabbaj.

For example, I transmit from my peer the ḥadīth, “Actions are only by intentions,” and he transmits from me the ḥadīth, “Allah does not accept the prayer of any one of you when he breaks wind until he performs ablution.” Such an exchange is mudabbaj. Likewise, if he reports from me the very ḥadīth I had taken from him—while I relate it through one chain and he relates it from me through another—that too is termed mudabbaj.

• Why is it called mudabbaj?
  They say the word is taken from dibājat al-wajh, meaning the cheek or side of the face, because each peer turns his face toward his companion to narrate, and the companion turns his face toward him to narrate in return, so that both have