What is the interpretation of the Hadith: "He who intercedes for his brother, and is given a gift for it, and accepts it, has indeed entered a great door among the doors of usury (riba)"?

The hadith mentioned in the question was narrated by Ahmad and Abu Dawud, and its wording is: "Whoever intercedes for someone and is given a gift, and he accepts it, then he has approached a great door of usury (riba)." Similar statements have been reported from the righteous predecessors (Salaf al-Salih).

Therefore, it is impermissible to accept anything in return for intercession (shafa'ah), a loan (qard), or a guarantee (daman), because accepting a gift for them diminishes their reward.

The meaning of the hadith is the prohibition of taking anything in return for a Muslim's intercession for his brother, because the Prophet (peace be upon him) commanded intercession, saying: "Intercede, and you will be rewarded." He also said: "Allah is in the aid of His servant as long as the servant is in the aid of his brother." And he said: "Whoever is able to benefit his brother, let him do so."

The prohibition applies when the gift is in return for intercession and the exertion of influence (bahl al-jah). However, if it is in return for effort and work, then there is no harm in it.