It is mentioned in the Quran that when Yûsuf ‘alayhis salâm became the king of Egypt and there was a drought, all his brothers came to him asking for food. (At that time they did not know that he was in fact their brother whom they had thrown into the well). He then revealed his true identity to them and gave them his shirt asking them to pass it over their father’s, Ya‘qûb’s ‘alayhis salâm, eyes. He also told them to return with everyone. As a result of passing his shirt over his father’s eyes, his eyesight returned to him. They then left their country and went to Egypt to meet Yûsuf ‘alayhis salâm. When they came to him, Yûsuf ‘alayhis salâm seated his father and his aunt onto his royal throne. He did this out of respect for them. It was at that time that the two of them and all his brothers fell into prostration before Yûsuf ‘alayhis salâm. In those days, such a prostration in place of salâm was permissible. This is no longer permissible.
As for the Quran mentioning this woman to be his mother – the actual fact is that his mother had passed away and Ya‘qûb ‘alayhis salâm had married this woman. Other scholars have stated that this incident is in regard to his mother whose name was Râhîl. When they prostrated to him, Yûsuf ‘alayhis salâm remarked: “This is the realization of my childhood dream.” He had seen a dream wherein the sun, the moon and 11 stars were prostrating to him.
Lesson: How pious this woman must have been for a prophet to pay his respects to her.