Origin of Title as-Siddiq for Abu Bakr (RA)
Jalal ad-Din as-Suyuti mentions the following in his book “The History of the Khalifahs”:
As for the name as-Siddiq, it is said about it, ‘He was given the affectionate nickname in the Jahiliyyah, because of the truthfulness for which he was known.’ It has been said also, ‘Because of his haste in affirming the Messenger of Allah, may Allah bless him and grant him peace, in that of which he informed.’
Al-Hasan al-Basri and Qatadah said: ‘The first time that he became known for it was the morning after the Night of the Isra’.
‘A’ishah, may Allah be pleased with her, said: ‘The idolaters came to Abu Bakr and said, ‘What do you think of your Companion? He claims that he was taken this night to Bait al-Maqdis (Jerusalem).’ He replied, ‘Did he say that?’ They said, ‘Yes.’ He said, ‘He has definitely told the truth. I believe and affirm him in matters more remote than that: the news from heaven in the early part of the morning and in the evening.’ For that reason he was called as-Siddiq.
Abu Hurairah said: When the Messenger of Allah, may Allah bless him and grant him peace, returned on the night in which he was made to travel (to Jerusalem), and he was at Dhu Tuwa, he said, ‘Jibril, my people will not believe me,’ He (Jibril) said, Abu Bakr will believe you, and he is as-Siddiq.’
An-Nazzal ibn Sabrah said: That man, Allah named him as-Siddiq on the tongue of Jibril and on the tongue of Muhammad, may Allah bless him and grant him peace. He was the deputy of the Messenger of Allah, may Allah bless him and grant him peace, for the prayer; he was contented with him for our deen and so we were pleased with him for our worldly affairs.
Abu Yaliya said: I cannot count the number of times that I heard ‘Ali say upon the mimbar, ‘Truly Allah named Abu Bakr through the tongue of His Prophet, a Siddiq”
Haldm ibn Sacd said: I heard ‘Ali say, and he swore upon it, ‘Allah definitely revealed from heaven the name of Abu Bakr, as-Siddiq.’ In the hadith of Uhud, ‘Be still, for there are only upon you a Prophet, a Siddiq and two martyrs*’
Abu Bakr’s mother was the daughter of his fathers paternal uncle (she was his father’s cousin). Her name was Salma bint Sakhr ibn ‘Amir ibn Ka’b. She was given the kunya (surname) Umm al-Khayr (Mother of good),’ said az-Zuhri.