Good manners dictate that you should reciprocate the one who does you a favour. The Prophet (peace and blessings of Allaah be upon him) enjoined that and said: “Whoever does you a favour, then reciprocate, and if you cannot find anything with which to reciprocate, then pray for him until you think that you have reciprocated him.” Narrated by Abu Dawood (1672); classed as saheeh by al-Albaani.
If you are not able to reciprocate with a gift, or helping with some task, or offering some service, etc, then at least you can say du’aa’ for him, and this du’aa’ may be a means of bringing him happiness in this world and in the Hereafter.
One of the best forms of du’aa’ for the one who has done you a favour is that which is mentioned in the Sunnah:
It was narrated that Usaamah ibn Zayd (may Allaah be pleased with him) said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Whoever has a favour done for him and says to the one who did it, ‘Jazak Allaahu khayran,’ has done enough to thank him.”
Narrated by al-Tirmidhi (1958) and by al-Nasaa’i in al-Sunan al-Kubra (6/53); classed as saheeh by al-Albaani in Saheeh al-Tirmidhi.
If you are not able to reciprocate with a gift, or helping with some task, or offering some service, etc, then at least you can say du’aa’ for him, and this du’aa’ may be a means of bringing him happiness in this world and in the Hereafter.
One of the best forms of du’aa’ for the one who has done you a favour is that which is mentioned in the Sunnah:
It was narrated that Usaamah ibn Zayd (may Allaah be pleased with him) said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Whoever has a favour done for him and says to the one who did it, ‘Jazak Allaahu khayran,’ has done enough to thank him.”
Narrated by al-Tirmidhi (1958) and by al-Nasaa’i in al-Sunan al-Kubra (6/53); classed as saheeh by al-Albaani in Saheeh al-Tirmidhi.
(Source: Islam QA)