Allāh’s Messenger (SAW) said, “None of you truly believes until he loves for his brother what he loves for himself.” (Bukhārī #13, Muslim #45) An important addition to the end of this ḥadīth is recorded by Nasāʾī, ‘of goodness.’
This is important because it helps us pinpoint the precise meaning of the words of Allāh’s Messenger (SAW). The word good covers all acts of obedience while excluding everything prohibited. We only want what is good for our brothers and sisters in faith, goodness as determined by Allāh and His Messenger (SAW).
And this leads to the next important point: it is also part of faith to hate for your brother what you hate for yourself of evil. This has not been explicitly mentioned in the ḥadīth because the love of something necessarily implies hatred of the opposite.
Therefore, true belief entails wanting all that is good for your brothers or sisters in Islām and hating all that is bad for them. It is to want the same for them that you would want for yourself; indeed, a higher level of faith is to want better or more for them.
(ʿIyād, Ikmāl al-Muʿlim 1:282, Ibn Ḥajr, Fatḥu’l-Bārī 1:58, Albānī, al-Ṣaḥīḥah 1:155)