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)
أَنَّ رَسُولَ اللهِ ﷺ قَالَ «مَنْ يَشْفَعْ لِأَخِيهِ شَفَاعَةً فَأَهْدَى لَهُ عَلَيْهَا هَدِيَّةً فَقَبِلَهَا فَقَدْ أَتَى بَابًا عَظِيمًا مِنْ أَبْوَابِ الرِّبَا»