It is reported that Al-Sha’bî – Allâh have mercy on him – said:

Allâh the Exalted distinguished Abû Bakr Al-Siddîq – Allâh be pleased with him – with four qualities He did not distinguish anyone else with: He called him Al-Siddîq (the true believer), and He never named anyone else Al-Siddîq; [Abû Bakr] was the companion of Allâh’s Messenger – praise and peace of Allâh be upon him – in the cave, and his companion during the Migration (Al-Hijrah); and Allâh’s Messenger – praise and peace of Allâh be upon him – told him to lead the prayer in the presence of the rest of the Muslims.

Abu Bakr Al-Daynûrî, Al-Mujâlasah wa Jawâhir Al-‘Ilm article 2815.