Imam as-San’aani (may Allah have mercy upon him) was asked about the reasons for the different wordings of Ahaadith which narrate one incident. So he responded with a work entitled, ‘The Treatise on the Differences in the Wordings of the Prophetic Hadith (رسالة في اختلاف ألفاظ الحديث النبوي)’.
In summary of his work, the reasons for the difference in the wordings of Ahadith on a single incident are the following:
1. There are a number of narrators from the Companions (may Allah be pleased with them) who narrated a specific incident that occurred multiple times [e.g. the wordings of the Ahaadith in relation to the Adhan, Tashahhud, and the descripton of the Prayer]. So this is easy to understand and poses no issue since each narrator reported the incident as it occurred at that time. So the Prophet (ﷺ) said or did something differently each time, hence the difference in wordings of the report
2. The incident is the same but the wordings are different (e.g. the Eclipse prayer which was reported with many different wordings despite it only occurring once in the life of the Prophet(ﷺ). So in this case, it is a must to examine the narrations and their chains of transmissions and determine which are the authentic from those which are weak. Then a person prefers the stronger view (based on the authentic narrations) over the weaker ones. This is a very difficult task to carry out except for the one whom Allah made it easy for from the People of Knowledge.
3. The Ahaadith are reported with different wordings in relation to one incident but their is no contradiction in them. Instead each narration provides an addition not present in the other (e.g. the narration of the man who prayed poorly. The narrations on how the Prophet (ﷺ) taught this man differ, but each provides an addition that is complementary and not contradictory). In this case, a person acts upon all of the reported narrations.
If a group of Companions (may Allah be pleased with them) narrate a specific incident and they differ in its wordings in terms of additions and subtractions, then it is due to one of two reasons:
1. That the narrator forgot some of the narration and narrated only part of it. Forgetfulness is something which afflicts mankind. Or the narrator did not narrate except what he heard (and he did not hear all of it, unlike another narrator). This might be due to him arriving late when the Prophet had already begun narrating the narration. So this narrator is truthful in what he narrated and all the Companions are trustworthy. So this explains why one narrator has additional wordings in his narration, while the other does not.
2. Reporting the narration by way of meaning. And this occurs a lot from the Companions and those who follow them. This is permissible for those who know the wordings of Ahaadith and their meanings. The majority of narrators do this. Allah preserved the Sunnah as He preserved the Book. So if a person examines all the narrations reported on specific an incident, he will arrive at the correct meaning intended by the Prophet (ﷺ).
There are other considerations, but these are the major ones which Imam as-San’aani (may Allah have mercy upon him) mentioned in this beneficial treatise.
And Allah Knows Best
Faisal bin Abdul Qaadir bin Hassan