I was wondering, in what conditions can a weak hadith become hasan? Does the weak hadith have to contain the exact same wording as another hasan hadith in order to be raised to the level of hasan?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, sallallaahu ʻalayhi wa sallam, is His Slave and Messenger.

The Hadeeth that is classified as Hasan Lighayrihi (Hasan due to other supportive reports reinforcing it) is the Hadeeth that is originally weak, but it has been reinforced by other supportive reports or versions narrated through different chains of narration (reinforcing one another) or corroborating narrations and upgraded to the level of Hasan Lighayrihi.

The conditions required for classifying a Hadeeth as Hasan Lighayrihi are the following:

1) It must not be very weak.

If the Hadeeth is very weak, it cannot be reinforced and upgraded to the degree of Hasan Lighayrihi. For instance, if a Hadeeth is declared weak because its chain of narration includes a narrator who was a dissolute, liar, or accused of lying and it was narrated through a different chain of narration of the same degree of weakness, it adds to its weakness.

The weak Hadeeth that may be reinforced and reclassified as Hasan Lighayrihi is the one whose weakness is due to the weak memory of one of its narrators who is truthful and pious or due to the interrupted chain of narration.

2) It should be reinforced by other supportive reports or versions reported through different chains of narration (reinforcing one another) or corroborating narrations; otherwise, a weak Hadeeth cannot be upgraded and reclassified as Hasan Lighayrihi.

3) Its other versions narrated through different chains of narration or corroborating narrations should be strong or slightly weak.

If its other versions narrated through different chains of narration or corroborating narrations are very weak as well, they do not reinforce it.

The corroborating narrations reinforcing such a weak Hadeeth must be to the same effect; the difference in the wording is irrelevant in this regard.

For more information, please, refer to Fatwa 13202.

Allah Knows best.