T h e A n s w e r : There are three aspects and three questions within this question.
First Aspect: For sure Abraham (Peace be upon him) was not equal to Muhammad (Peace and blessings be upon him), but his family or descendants were prophets. Muhammad’s (Peace and blessings be upon him) family were saints, and saints cannot reach the level of the prophets. Evidence that this prayer for his family has been accepted in shining fashion is this:
The fact that the saints who, among three hundred and fifty million, emerged from the progeny of only two of the Family of Muhammad (PBUH), that is, Hasan (May God be pleased with him) and Husayn (May God be pleased with him), were in the great majority of cases the spiritual guides and leaders of the sufi paths of reality, was because they received the effulgence of the Hadith: “The learned of my community are like the prophets of the Children of Israel.”1 Those who guided the greater part of the Umma to the way of truth and reality of Islam —foremost Ja‘far al-Sadiq (May God be pleased with him), Gawth al-A‘zam (May God be pleased with him), and Shah Naqshband (May God be pleased with him)— were the fruits of the acceptance of this prayer for Muhammad’s (Peace and blessings be upon him) Family.
Second Aspect: The reason for benedictions of this sort being restricted to the ritual prayers is that they recall to one that he is on the way opened up and taken by the great caravan of the prophets and saints, who are the most luminous, perfect, and righteous of mankind and its eminent members. He has joined that vast congregation, which acquires strength through its hundredfold consensus and cannot confuse its way, and is accompanying it on the straight path. By recalling this, he is saved from satanic doubts and delusions. Evidence that the members of this caravan are the friends and acceptable creatures of the universe’s Owner, and its opponents and enemies are rejected, is that from the time of Adam, succour has always arrived from the Unseen for the caravan, while its opponents have always been visited by heavenly calamities.
Yes, just as opponents like the people of Noah, the Thamud and the ‘Ad, Pharaoh and Nimrod have all received blows from the Unseen that tell of Divine wrath and chastisement; so the sacred heroes of the mighty caravan, like Noah (Peace be upon him), Abraham (Peace be upon him), Moses (Peace be upon him), and Muhammad (Peace and blessings be upon him), have wondrously and extraordinarily manifested miracles and
al-‘Ajluni, Kashf al-Khafa, ii, 64; Tecrid-i Sarîh Tercemesi (Turk. trans.) Diyanet Isleri, i, 107.