Abu Bakr (Abdullah ibn Abi Quhafa) (Arabic: عبد الله بن أبي قحافة, Transliteration: ʿAbd Allāh ibn Abī Quḥāfah, c. 573 CE - 634 CE) also known as Abū Bakr as-Șiddīq (Arabic: أبو بكر الصديق) was a senior companion (Sahabi) and the father-in-law of the Islamic prophet Muhammad. He ruled over the Rashidun Caliphate from 632–634 CE when he became the first Muslim Caliph following Muhammad's death. As Caliph, Abu Bakr succeeded to the political and administrative functions previously exercised by Muhammad, since the religious function and authority of prophethood ended with Muhammad's death according to Islam. He was called Al-Siddiq (The Truthful) and was known by that title among later generations of Muslims.

As a young man, Abu Bakr became a cloth merchant and he traveled extensively in Arabia and neighboring lands in the Middle East, through which he gained both wealth and experience. He eventually came to be recognized as the chief of his clan. On his return from a business trip to Yemen, he was informed that in his absence Muhammad had openly declared his prophethood. Not long after, Abu Bakr accepted Islam and was the first person outside the family of Muhammad to openly become a Muslim. He was instrumental in the conversion of many people to the Islamic faith and early in 623, Abu Bakr's daughter Aisha was married to Muhammad, strengthening the ties between the two men.

Shaykh Abu Bakr Shibli (861 - 946) was an important Sufi of Persian descent, and a disciple of Junayd Baghdadi.

He was born in Baghdad or Samarra, although his family was originally from Khorasan in Persia. He was a high official of Baghdad before he embarked on the spiritual path and became a disciple of Junayd Baghdadi. His name is mentioned by the Persian poets Attar, Rumi and Sanai. He was also associated with Hallaj. According to one source, he was in a constant state of jadhb and was finally committed to an asylum. Others assert that he feigned madness.

Attributed to him is the saying: "O people! I go to place beyond which these is no beyond. I go to the south and the north, to a place beyond which is there is no beyond. Everything that I saw after that I could see in one hair of my little finger."

Shibli was imprisoned many times by the Caliph despite his influence and enormous wealth. Shibli went into self-imposed exile and began searching for divinity. Meanwhile, in the Sultanate, the Caliph realised that Shibli had not committed any wrongdoing and a search party was sent out to find him. The ministers were carrying a set of royal robes that the Caliph had sent for Shibli. They offered it to Shibli saying that a decree had been passed reinstating him and that he could return without fear of being prosecuted. Shibli took the robes and wiped his sweating face with them.