"وَاعلَم يَا بُنَيَّ أنَّ اَحَداً لَم يُنَبِّئ عَنِ الله كَمَا اَنبَأ عَنهُ الرَّسُولُ صَلّى الله عَلَيهِ وَآلهِ، فَارضَ بِهِ رَائِداً وَاِلى النَجَاة قَائِداً فَانّي لَم اَلُكَ نَصِيحَةً وَاِنَّكَ لَن تَبلُغَ في النَّظَرِ لِنَفسِكَ وَاِن اِجتَهَدتَ مَبلَغَ نَظَرِي لَكَ"
“Know, my son, that no one has told us of Allah like the Prophet (S) has. Thus, be content with him as a leader and as a guide to salvation. Indeed, I have not fallen short in advice to you, and, however much you may strive, you will never attain that degree of concern for your welfare that I have for you”.
In this part of the letter, Imam ‘Ali (as) emphasizes two points:
As we know that the prophets have been sent to people at different times and under different conditions. The more backward the people, the simpler was the prophets' training and educating people. Their schedules were like those of present-day schools where in elementary schools simpler books and methods are used whereas in the high schools we have more complicated programs.
Since the more ancient Prophets were sent to people who had not progressed enough, their methods of educating people were more elementary, but since the Prophet of Islam was the last of the Prophets,1 and his religion is eternally the way of life for all men,2 there it is better to be said that "nobody has told us of Allah like the Prophet (S) has", and his religion is the most comprehensive of all religions.3 Anybody adopting another way of life is rejected.4 It is also right to say: Only he is to be chosen as the leader5 since his religion is the most comprehensive, his leadership the most perfect and his commandments the most beneficial.
Every father wishes well for his child. He will not spare any advice in building his personality. He is usually more decisive, determined and experienced than the young one who usually possesses less experience. It is an old saying that an old one sees in the mud brick what the young one can see in the mirror.
Concerning the value of the ideas and thoughts of the aged, Imam as-Sadiq (as) has said: "The existence of an elderly one in his family is like the Prophet among his people".6
And this is a fact. On the one hand, there is a father like Imam ‘Ali (as), who is the gate of knowledge for the Prophet (S), and who is well-experienced, and on the other hand, there is a child from the Prophet's Household, who is going to guide the Islamic world in the near future, and be the substitute for his father in the guidance of the Muslim world. Therefore, for these valid reasons it is necessary that, firstly, sufficient amount of advice be given him, and secondly, it was suitable for Imam ‘Ali (as) to employ his own experiences in the education of his son.
"وَاعْلَم يَا بُنَيَّ اِنَّه لَو كَانَ لِرَبِّكَ شَرِيكٌ لاَتَتكَ رُسُلُه وَلَرَأيتَ آثَارَ مُلكِهِ وَسُلطَانِهِ وَلَعَرَفتَ اَفعَالَهُ وَصِفَاتَه وَلكِنَّهُ اِلهٌ وَاحِدٌ كَمَا وَصَفَ نَفسَهُ لا يُضَادُهُ في مُلكِهِ اَحَدٌ وَلا يَزُولُ اَبداً وَلَم يَزَل اَوَّلٌ قَبلَ الاَشيَاءِ بِلا اَوَّلِيةٍ وَآخِرٌ بَعدَ الاَشْياَء بِلا نِهَايَة عَظُمَ عَن اَن تَثْبُتَ رُبُوبِيَتِه بِاحَاطَةِ قَلبٍ اَو بَصَرٍ فَاِذَا عَرَفتَ ذَلِكَ فَافعَل كَمَا يَنبَغِي لِمثلِكَ اَن يَفعَلَهُ في صِغَرِ خَطَرِهِ وَقِلَّةِ مَقدِرَتِهِ وَكَثْرَةِ عَجْزِهِ وَعِظَمِ حَاجَتِهِ اِلى رَبِّهِ في طَلَبِ طَاعَتِهِ وَالخَشْيَةِ مِن عُقُوبَتِهِ وَالشَفَقَةَ مِن سَخَطِهِ فَاِنَّهُ لَم يَامُركَ اِلا بِحُسْنٍ وَلَم يَنْهَكَ اِلا عَن قَبِيحٍ"
“Know, my son! If there were an associate for your Lord, his Prophets would have come to you and you would have observed the signs of his dominion and his rule and you would have recognized his acts and attributes. But He is One, as He has described Himself. None opposes Him in His sovereignty. He never ceases to be and He is eternal. He is the First before all things, without any beginning, and the Last after all things, without any end. He is far greater than that His Divinity be proved through the comprehension of the heart or the eye. When you realize that, then act as it befits one such as you to act – one with his insignificance, his weakness, his incapacity and his tremendous need of his Lord in seeking His obedience, dreading His chastisement and fearing His anger, for He does not command you anything but good, and does not forbid you from anything but evil”.