Abu Mūsa al-Ash‘ari (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "An honest Muslim storekeeper, who carries out the orders of his master and pays fully what he has been ordered to give with a good heart and pays to that person to whom he was ordered to pay, is regarded as one of the two charitable persons."
A trustee who is Muslim and honest and who carries out what is assigned to him, willingly and cheerfully, will be regarded as one of the two givers of charity. He should be Muslim, for if he is non-Muslim and honest, carrying out what is assigned to him, still he will not be rewarded for that, since non-Muslims will not obtain rewards in the Hereafter for their good deeds. Allah, the Almighty, says: {And We will regard what they have done of deeds and make them as dust dispersed} [Sūrat al-Furqān: 23]. He also says: {And whoever of you reverts from his religion [to disbelief] and dies while he is a disbeliever - for those, their deeds have become worthless in this world and the Hereafter, and those are the companions of the Fire, they will abide therein eternally} [Sūrat al-Baqarah: 217]. If a person performs good deeds and then converts to Islam, he will be rewarded for those past deeds. So, he should be Muslim and honest and should execute what is required of him, and finally he should do so willingly and cheerfully; in other words, he should not mistreat those he gives or remind them of the favors done to them. In this way, he will be regarded as one of the two givers of charity, though he has given nothing from his own money.