Al-Bara' bin 'Azib said:"The Messenger of Allah commanded us to do seven things: He commanded us to attend funerals, visit the sick, to reply (say: Yarhamuk Allah [may Allah have mercy on you]) to one who sneezes, to accept invitations, to support the oppressed, to fulfill oaths (when adjured by another) and to return greetings of Salaam."
أَخْبَرَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، وَمُحَمَّدُ بْنُ بَشَّارٍ، عَنْ مُحَمَّدٍ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنِ الأَشْعَثِ بْنِ سُلَيْمٍ، عَنْ مُعَاوِيَةَ بْنِ سُوَيْدِ بْنِ مُقَرِّنٍ، عَنِ الْبَرَاءِ بْنِ عَازِبٍ، قَالَ أَمَرَنَا رَسُولُ اللَّهِ صلى الله عليه وسلم بِسَبْعٍ أَمَرَنَا بِاتِّبَاعِ الْجَنَائِزِ وَعِيَادَةِ الْمَرِيضِ وَتَشْمِيتِ الْعَاطِسِ وَإِجَابَةِ الدَّاعِي وَنَصْرِ الْمَظْلُومِ وَإِبْرَارِ الْقَسَمِ وَرَدِّ السَّلاَمِ .
Nesai
The Book of Oaths and Vows • Hadith 3778