A whole life of service, austerity and devotion of a non-Ṣaḥābī will not compare with a small action of a Ṣaḥābī, Companion of the Prophet, which he did, when Islam was weak and Muslims were few, in order to promote the cause of Islam and help the Prophet [صلى الله عليه وسلم]. Addressing the people who embraced Islam later, the Prophet once said: ‘If you spend in God’s way a heap of gold equal to the mountain Uḥud, it will not be equal to a mudd (roughly a kilo) of wheat which my comrades have spent, nor even half a mudd.’ [Saḥīḥ Muslim, Sunan al-Tirmidhī and Musnad Aḥmad] This explains the greatness of Abū Bakr as against every other Ṣaḥābī. He is the first of the first Muslims who responded to the Prophet’s call and believed in him, devoted their lives, spent their wealth and rendered great services to Islam. This is the reason why the Qur’an says: ‘You are not equal to those who spent money before the Conquest (of Makkah) and fought. However, God promised good reward to both.’ [57:10]
Some people seeing the merits and honours of others have hesitated to recognise the superiority of Abū Bakr over all the Companions of the Prophet. They do not know that if merits and devotions were the criterion of superiority, some individual followers of a prophet who had more merits and devotions would have been superior to their prophets, who did not have much of these things. It is obvious, therefore, that the criterion of superiority is something other than meritorious acts and devotions. In my humble opinion, the criterion lies in the fact as to who is the first in defending religion, in spending money and energy in its cause, and working for its triumph. Since the prophet excels his whole community in these matters, he is the best of them all. For similar reasons any one of the community who excels in these matters is better than the others. Those who are forerunners in religion are the teachers and guides to their followers; the latter profit from their services and their merits. In our community the greatest man after the Prophet is Abū Bakr Ṣiddīq [رضي الله عنه], for he was first in spending money and property, the first in preaching and struggle, the first in staking his life and honour for religion, the first in fighting untruth and evil, the first in assisting the Prophet, and the first in making Islam victorious. His superiority over all others is well established.
[Maktubāt, Vol. II:99. English translation by Muhammad Abdul Haq Ansari in Sufism and Shari‘ah, Leicester: Islamic Foundation, 1986, pp. 243-244]