Since caliphate was assigned to him...

Since caliphate was assigned to him, the commander of the faithful experienced the ugliness of its taste, the weight of its burdens, the hardship of its tasks, and the extent of obedience to God and fear of Him by the one who accepts to bear its responsibility; so he exhausted his body, remained awake and prolonged his contemplation upon whatever would bring about the dignity of the creed, the conquering of the polytheists, the good of the nation, the dissemination of justice, the upholding of the Book and the Sunnah, and all of this forbade him from relaxing or resting or enjoying life, knowing that God will hold him accountable for all of these matters, and out of his own love to meet his Lord after having advised them regarding His religion and servants, selecting his heir for the best interest of the nation after him the best person he can choose due to his piety, soundness of belief and knowledge, the most suited among them to carry out God's commandments and His injunctions, pleading the Almighty to help him and inspire to him what brings about His Pleasure and Obedience to Him at night and at day, earnestly pleading and praying, from among his own household the descendants of Abdullah ibn al-Abbas and Ali ibn Abu Talib (a.s.), keenly discerning their condition, belief and knowledge, inquiring about what he did not know regarding them, till he came to know their conditions on a first-hand basis, observing them personally and examining their affairs, questioning them about what he did not know in their own regard.

Having prayed God for guidance in making his decision, exerting himself in carrying out His commandments regarding His servants and lands in both households, he selected Ali ibn Musa ibn Ja’far ibn Muhammad ibn Ali ibn al-Husayn ibn…