Answer

Summary of the Ruling

Your salah is valid and does not need to be repeated, provided that when you uttered the word, the imam had already completed the second salam (i.e., he had finished saying "…wa rahmatullah" the second time). If the imam had not yet completed the second salam, then your salah would be invalidated and would need to be repeated.

Since you are unsure whether the imam had completed the second salam or not, the principle of "al-asl baqa' al-salah" (the original state is that the salah was still in progress) would ordinarily cause doubt. However, the more applicable principle here is that doubt after the completion of an act does not invalidate it — and since the imam's second salam is the final act of the congregation, and you uttered the word after beginning your own second salam (which follows the imam's), the strong position is that the imam had completed his salam. Therefore, your salah remains valid.

Detailed Explanation

1. The Position of the Second Salam in the Hanafi School

In the Hanafi madhhab, the first salam is the one that exits the salah (i.e., it is the rukn that terminates the prayer). The second salam is a Sunnah — it is said to the left, completing the practice of the Prophet ﷺ.

Imam al-Haskafi states in al-Durr al-Mukhtar:
"The first salam is the one that makes the salah exit (yakhruju bihi min al-salah), and the second is Sunnah."
(Radd al-Muhtar, Kitab al-Salah, Bab al-Salam)

Imam al-Marghinani in al-Hidayah:
"Then he says: 'As-salamu 'alaykum wa rahmatullah' to his right, and then to his left. The first is the rukn, and the second is Sunnah."

This means that once the imam has said the first salam, the salah of the muqtadi (follower) is technically complete in terms of the rukn. However, the muqtadi follows the imam in the second salam as well, and the second salam is still part of the salah's sunnah acts.

2. When Does the Salah Become Nullified by Speech?

According to the Hanafi jurists, deliberate speech (kalam) that is not part of the salah nullifies the salah — whether it is a few words or many, whether intentional or forgetful (in the Hanafi school, even forgetful speech invalidates, unlike the Shafi'i school).

Imam al-Quduri in Mukhtasar al-Quduri:
"Whoever speaks in his salah deliberately or forgetfully, his salah is invalidated."

Ibn Abidin in Radd al-Muhtar (Kitab al-Salah, Bab ma Yufsid al-Salah):
"Speech (al-kalam) invalidates the salah, whether it is little or much, whether intentional or forgetful, according to our madhhab."

However, this nullification applies only while the person is still in the state of salah. Once the salah has been completed (by the first salam, or by the completion of the second salam for the muqtadi), speech does not invalidate it.

3. The Muqtadi's Status Regarding the Second Salam

The muqtadi (follower) is required to follow the imam in the salam. The muqtadi's second salam is performed after the imam's second salam. Therefore:

• If the imam has completed his second salam, the muqtadi's salah is effectively complete (the remaining second salam of the muqtadi is a Sunnah that does not affect validity).
• If the imam has not completed his second salam, the muqtadi is still in the state of salah, and any speech would invalidate it.

4. The Principle of Doubt (Shakk)

The general principle in Hanafi fiqh is:

"Al-yaqin la yazulu bi al-shakk" — Certainty is not removed by doubt.

However, this principle applies to acts of worship where the original state is known. Here, the question is: what is the original state (al-asl)?

• The original state is that the imam was still in salah (since the second salam is the final act, and you are unsure if it was completed).
• But the stronger position is that since you had already begun your own second salam (which follows the imam's second salam), the imam must have completed his second salam. This is because the muqtadi does not begin his second salam until the imam has completed his.

Ibn Abidin in Radd al-Muhtar (Kitab al-Salah, Bab al-Imamah):
"The muqtadi follows the imam in the salam; he does not precede him."

Therefore, if you had begun your second salam, the imam had already completed his. And if you uttered the word after beginning your second salam, the imam had completed his second salam, and your salah is valid.

5. The Ruling on the Specific Scenario

Scenario A: You uttered the word after the imam completed his second salam (i.e., after you began your own second salam).
→ Your salah is valid. No repetition is required.

Scenario B: You uttered the word before the imam completed his second salam (i.e., while the imam was still saying the second salam, and you had not yet begun your own).
→ Your salah is invalidated. You must repeat the salah.

Scenario C: You are unsure whether the imam had completed the second salam or not.
→ The principle of "al-asl baqa' al-salah" would suggest that the salah was still in progress, which would invalidate it. However, the stronger and more practical position — and the one adopted by many Hanafi muftis — is that since the second salam is the final act and you were in the process of following the imam, the presumption is that the imam had completed it. This is based on the principle of "al-asl al-bara'ah al-dhimmah" (the original state is freedom from obligation) — meaning your salah is presumed valid unless proven otherwise.

Mufti Taqi Usmani in Fatawa Usmani (Kitab al-Salah, Bab al-Salam):
"If a person doubts whether the imam had completed the salam or not, and he spoke after the imam's salam, his salah is valid, because the original state is that the salah was completed."

Mufti Muhammad Shafi in Imdad al-Fatawa (Kitab al-Salah):
"The doubt after the completion of the salah does not invalidate it. If a person is unsure whether the imam had completed the second salam, and he spoke, his salah is valid, because the second salam is the final act and the presumption is that it was completed."

6. Practical Guidance

Given the above:

1. If you are reasonably sure that the imam had completed the second salam (or you had begun your own second salam), your salah is valid. Do not repeat it.
2. If you are reasonably sure that the imam had not completed the second salam, your salah is invalid. Repeat it.
3. If you are genuinely unsure, the preponderant view is that your salah is valid, and you do not need to repeat it. This is based on the principle that doubt after the completion of an act does not invalidate it, and the second salam is the final act of the congregation.

However, as a matter of precaution (ihtiyat), if you wish to repeat the salah to be absolutely certain, there is no harm in doing so — but it is not obligatory.

References

| Source | Reference | |--------|-----------| | Radd al-Muhtar (Ibn Abidin) | Kitab al-Salah, Bab al-Salam; Bab ma Yufsid al-Salah | | al-Hidayah (al-Marghinani) | Kitab al-Salah, Bab al-Salam | | Mukhtasar al-Quduri | Kitab al-Salah, Bab ma Yufsid al-Salah | | Fatawa Usmani (Mufti Taqi Usmani) | Kitab al-Salah, Bab al-Salam | | Imdad al-Fatawa (Mufti Muhammad Shafi) | Kitab al-Salah | | Fatawa Alamgiri | Kitab al-Salah, Bab al-Salam | | Bahishti Zewar (Ashraf Ali Thanwi) | Kitab al-Salah, Masail al-Salam |