The Story of repairing the Wall
Allah tells:
فانطلقا
they both proceeded,
after the first two instances,
حتى إذا أتيا أهل قرية
till when they came to the people of a town,
Ibn Jarir narrated from Ibn Sirin that this was Al-Aylah.
According to the Hadith;
حتى إذا أتيا أهل قرية لياما
When they came there, the people of the town were mean. i.e., miserly.
استطعما أهلها فٲبوا أن يضيفوهما فوجدا فيها جدارا يريد أن ينقض فٲقامه
they asked them for food, but they refused to entertain them. Then they found therein a wall about to collapse and he (Khidr) set it up straight.
means, he fixed it so it was standing upright properly.
We have already seen in the Hadith quoted above that he set it up with his own hands, supporting it until it was standing straight again, which is something extraordinary.
At this point,
قال لو شيت ﻻتخذت عليه أجرا
(Musa) said: If you had wished, surely you could have taken wages for it!
meaning, because they did not entertain us as guests, you should not have worked for them for free