Imam al-Baqir(A.S.) designated al-Sadiq(A.S)
Imam Mohammad Baqir (A.S), designated his son al-Sa`diq, peace be on him, as an Imam. For al-Sadiq was the pride of the world. He was the pioneer of culture and science in Islam. His father designated him to be an Imam and successor and general authority for the community after him. He said to his followers that it was incumbent on them to follow and obey his son.
Imam Mohammad Baqir (A.S), lauded his son, Imam al-Sa`diq, peace be on him. He gave an explicit designation for his Imamte. Abu` al-Saba`h al-Kina`ni reported. He said: [Abu` Ja'far Mohammed looked towards his son Abu` 'Abd Allah (al-Sa`diq), peace be on him, and said (to us): "Do you see that man? He is one of those of whom Allah, the Mighty and High, said: We wish to grant a favor to those who have been humiliated in the land and We will make them Imams and inheritors.(Usul al-Kafi, vol. 1, p. 306).
Ali b. al-Hakam reported on the authority of Ta`hir, who said: I was with Imam Mohammad Baqir (A.S),
When Ja'far (al-Sa`diq) approached, Imam Mohammad Baqir (A.S), said: "Here is the best of creatures". (Usul al-Kafi, vol. 1, p. 306 )
His Testamentary Enjoinments
Imam Mohammed Baqir(A.S), gave several enjoinments to his son, Imam al-Sa`diq(A.S),. Among them are the following:
1. He said: "Ja'far, I give testamentary enjoinments to you (to treat) my followers well." So, Ima`m al-Sa`diq, peace be on him, replied: "May I be your ransom, I will make them (know their religion so well) that any man among them in the country will not (have to) ask any one (for advice). (Usul al-Kafi, vol. 1, p. 306).
He, peace be on him, enjoined his son to spend (money) on them and to take care of their affairs to make them devote themselves to seek knowledge, to record his traditions, and to spread his sciences and morals among the people.
2. He, peace be on him, enjoined his son al-Sa`diq, peace be on him, to shroud him in the cloak in which he used to perform the prayer. (Safwat al-Safwa, vol. 2, p. 63. Ibn al-Wadi, Tarikh, vol. 1, p. 184. Abi al-Fida', Tarikh, vol. 1, p. 214. Ibn al-Jawzi, al-Muntazam, vol. 7)
He wanted that to be a truthful witness with Allah for his great worship and his obedience to Him.
As for the text of his testamentary enjoinments, it was reported by Imam Sadiq(A.S), who said: When my father was near to death, he said (to me): "Call witnesses for me."
I summoned four men from Quraysh, among them Na`fi', retainer of 'Abd Allah b. 'Umar. Imam Baqir (A.S) told them: "Write this testimony which I bequeath (like) Jacob did to his sons: My sons, Allah has chosen the religion for you. So, do not die except as Moslems.
He orders him to shroud him in his cloak in which he used to perform the Friday prayer, to put his turban on him, to make his grave a square, to raise it the height of four fingers above the ground, and to take his shabby clothes away from him at his burial.
Then he said to the witnesses: "Depart, may Allah have mercy on you."
Imam Sadiq asked Imam Baqir(A.S) after the witnesses had gone, "why there was a need to have witnesses for the testimony?"
Imam Baqir(A.S) replied "My son, I did not want people to say later that no testimony was made, I wanted you to have proof."
(Usul al-Kafi, vol. 1, p. 307)