It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Holy Prophet (peace and blessings be upon him) said: Every Muslim has six rights over another Muslim: (1) When you meet him, greet him with Salam; (2) If he sneezes, respond to him; (3) If he invites you, accept his invitation; (4) If he falls ill, visit him; (5) If he dies, attend his funeral; (6) Wish well for him behind his back.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 8271
Hadith Gradingحکم دارالسلام:حديث صحيح، خ: 1240، م: 2162، فى هذا الإسناد ضعف، عبدالله فيه لين