The Prophet ﷺ said: If anyone intercedes for his brother and he presents a gift to him for it and he accepts it, he approaches a great door of the doors of usury. (Using translation from Abū Dāʾūd 3541)
قَالَ رَسُولُ اللهِ ﷺ «مَنْ شَفَعَ لِأَخِيهِ شَفَاعَةً فَأَهْدَى لَهُ هَدِيَّةً فَقَبِلَهَا فَقَدْ أَتَى بَابًا عَظِيمًا مِنَ الرِّبَا»