Ali (may Allah be pleased with him) relates that he heard the Holy Messenger (peace and blessings of Allah be to him) say: “When a Muslim visits an ailing Muslim in the morning, seventy thousand angels keep invoking blessings for him till the evening. And if he visits him in the evening, seventy thousand angels keep invoking blessings for him till the morning, and he is allotted an orchard of fruit trees in the Paradise.” (Tirmidhi)
Every noble deed is universally acknowledged as desirable and worth doing. But it is the distinction of Islam that it rewards believers manifold even for one single noble deed performed by him. A hadīth bears testimony to the fact that when a Muslim intends to do some noble deed, he earns one reward. And, when he translates his intention into action, he is rewarded ten-fold. Such is the bounty of Allah the Almighty, the Most Merciful.
In the hadīth under study the Holy Messenger (peace and blessings of Allah be to him) encourages the believer to visit his ailing brother. He gives him glad tidings that if he visits an ailing Muslim in the morning, seventy thousand angels will keep invoking blessings for him till the evening. And, if he visits him in the evening, the same number of angels will keep invoking blessings for him till the morning. As a result he is blessed with an orchard of fruit trees in the Paradise.
His visit may or may not benefit the ailing brother. But he will be rewarded in the Paradise manifold.