The knowledge of lineage is for God; Because only He is aware of the reality of matrimonies and born, and others only know its appearance, and God grants this knowledge to anyone of His Caliphs, who He wills; According to Mutiwatir narrations, He granted to His prophet (PBUH), when he became angry with many improper and unnecessary questions of his companions and said: “Whoever wants to be known of his lineage, ask me to inform him”! So Abdullah ibn Hadhafay Sahmi, in which there was a doubt about his lineage, asked: “Who is my father?” his Excellency said: “Your father is Hadhafay Sahmi”! Abdullah said: «اَللَّهُ أَكْبَرُ الَّذِي أَثْبَتَ نَسَبِي عَلَى لِسانِ نَبِيِّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ»; “The God is great, who proved my lineage by the words of His prophet (PBUH)”! Then another man asked: “who is my father”?! His Excellency said: “your father is freed Salim of Shibah”. In that moment, some companions of his Excellency became worry, and asked him for forgiveness and to suppress his anger and give up such a work, with the excuse that «إِنَّهُ لا عِلْمَ لَنا بِما صَنَعَتِ النِّساءُ فِي خُدُورِها»; “We are not aware of what the women have done behind the curtains”! Then his Excellency accepted their excuse and suppressed his anger and came down from the pulpit. Such a knowledge for the Caliphs of his Excellency as a legacy from him has also been narrated. From here it is understood that the truth of the lineages is only apparent for God, and its certainty is not possible except through His Caliph on earth; Especially in the present time, in which many generations have been passed from the prophet (PBUH) and tribes and people are intertwined, and because of fears and greed many Hashemite are counted as non-Hashemite and many non-Hashemite are counted as Hashemite.
Of course, certainty is not necessary about the truth of lineage in laws such as inheritance and payment of khums, and its assurance, according to Estefazeh or genealogy, is enough, except in the issues of belief such as believing in the Caliphate of a person, in which it is necessary to make certain about his Hashemite, and it reaches by a definite news from the previous Caliph or an evident sign from God, not with factors such as Estefazeh or genealogy; Because factors such as Estefazeh or genealogy leads to conjecture, and conjecture is not enough for such a belief. Yes, in the case that God or His former Caliph announces a definite news about someone's caliphate, the certainty of his lineage will be reached by the way of the certainty of his caliphate; because those two are related.
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