From Abu Hamzah Anas ibn Malik (رضي الله عنه), the servant of the Messenger of Allah (صلى الله عليه وسلم), from the Prophet (صلى الله عليه وسلم), that he said, “None of you believes until he loves for his brother what he loves for himself.” Al-Bukhari and Muslim narrated it.
With respect to his saying (صلى الله عليه وسلم),“None of you believes until he loves for his brother what he loves for himself,” the first thing to be said is that it should be interpreted in terms of the universality of brotherhood even to the extent of encompassing disbelievers and Muslims. One loves for one’s disbelieving brother what one loves for oneself; his entrance into Islam, just as one loves for one’s Muslim brother his continuance in Islam. For this reason supplication for a disbeliever’s guidance is recommended. The hadith proves the incompleteness of the iman of whoever does not love for his brother what he loves for himself.
What is meant by ‘love’ is ‘willing good and benefit’, moreover what is meant is love in terms of the deen and not human love, for human nature may dislike [another’s] attainment of good and another’s being distinguished over oneself. Man must oppose human nature, supplicate for his brother and wish for him that for which he himself wishes. If a person does not love for his brother what he loves for himself he is envious.
[Imām Yaḥyā bin Sharaf al-Dīn al-Nawawī, الأربعون النووية في الأحاديث النبوية [Al-Arba‘īn al-Nawawīyyah fi al-Aḥādīth al-Nabawīyyah] English translation: The Complete Forty Hadith by Abdassamad Clarke, Ta-Ha Publishers, London, 2000, pp. 62-63 (translator’s notes omitted)]