Al-Ḥārith goes with Abū Zayd to collect what the members of the gathering had promised. The story moves briskly from a night of emotional persuasion to a morning of practical payment.
At this point their immediate task is collection, not verifying the family relationship. Al-Ḥārith accompanies Abū Zayd and helps the process reach its intended end.
The later revelation is therefore doubly striking. Al-Ḥārith has not merely heard the story: he has helped bring about the financial result, before discovering that the central claim rested on deception.
«فَوَصَلْتُ جَنَاحَهُ»
Thus I strengthened his wing—giving him practical support.
The wing metaphor describes the narrator’s aid, not a literal attempt to reach the supposed son.