Sayyiduna Anas bin Malik (may Allah be pleased with him) narrated: the Prophet (peace and blessings be upon him) said: "Whoever shows kindness to a believer, or goes out for him in any of his needs, whether that need is small or great, it is binding upon Allah Almighty to grant him a servant from among the servants of Paradise."
Al-Bazzar recorded it; its chain contains a narrator, Mu'alla bin Maymun, who is matruk (abandoned).