There are a variety of ideas on this subject...

There are a variety of ideas on this subject, but the most famous commentary among the scholars is the following: Once the Prophet (S) was deeply engaged in trying to explain the Holy Qur'an to some pagan Quraish leaders such as 'Atabat‑ibn‑i‑Rabi 'ah, Abu‑Jahl, 'Abbas‑ibn‑'Abdul‑Mutallib and some others. He was hopeful that it would attract them to Islam, and in so doing, surely a lot of others would come to Islam, too. And therefore, put an end to their sabotage.

But, suddenly, he was interrupted by a blind man; ‘Abdullah‑ibn‑Ummi‑Maktum, who was apparently poor, so that no one took notice of him. He wanted to learn the Qur'an and asked the Prophet (S) to teach him. He repeated his statement again and again, because he did not know exactly whom he was talking to. The Holy Prophet (S) naturally did not like the frequent interruptions and this was seen on his face.

“These Arab leaders”, he said to himself “may think of Muhammad as a Prophet of the poor and the blind." Then he turned away from 'Abdullah and continued the work at preaching Allah’s Message to them. At that moment he received the new verses stated above, which admonished the Prophet (S) for this action.

Afterwards, he always held 'Abdullah in high honor, and whenever he saw him he used to tell him “Hail to the one for whom Allah admonished me.” And, then, he questioned the man: “Is there anything that I can do for you?” The blind man became a true and sincere Muslim and as a direct appointment by the Prophet, himself, become a governor of Medina on two occasions when the Prophet (S) went to battle.

A second opinion about this revelation is given for these verses, which is that a man from the Umayyads was sitting with the (S) when 'Abdullah‑ibn Ummi‑Maktum arrived. When this man saw 'Abdullah, he frowned and turned his back to him, as if he might become infected by him. The aforementioned verses were about the man sitting with the Prophet (S) and the admonishment was for him.

It has been narrated that Imam Sadiq (as) agreed with this opinion when he was asked about this occasion of revelation. The late Sayyed Murtaza, the great scholar of Islam, approved with this occasion of revelation, as well. There is nothing, of course, in the verse, itself, to show clearly that the one who is addressed is Muhammad (S).