Is the rich obligated to respond to the poor if he offers him a gift intending help, and is there evidence for that in the Quran or Sunnah, and what are the cases that necessitate responding to or returning gifts?

A "hibat ath-thawab" (gift for recompense) is when a person gives a gift to another, hoping for a return from them. If recompense is stipulated in the gift contract, then it becomes obligatory. However, if the gift is absolute, scholars differ regarding the intention for recompense (thawab): The Shafi'is do not consider recompense if the person gifts to someone lower, higher, or equal in status. The Malikis believe the giver's intention unless there is a customary impediment. The Hanafis and Hanbalis do not consider recompense unless it is stipulated.

Evidence for its permissibility is drawn from the verse: "And whatever you give for interest to increase thereby in the wealth of people will not increase with Allah" (Quran 30:39), which the Companions and Tabi'un interpreted as referring to hibat ath-thawab. Also, from the hadith: "Whoever gives a gift, he has more right to it as long as he is not recompensed for it."

If a poor person gives a gift to a rich person with the intention of recompense, whether by stipulation or custom, then it is obligatory for the rich person to recompense them or return the gift.