It is narrated from Sayyiduna Anas (may Allah be pleased with him) that he said: A man passed by the Prophet (peace and blessings be upon him), and another man (who was present) said: "I love him for the pleasure of Allah." The Prophet (peace and blessings be upon him) said: "Have you told him?" He said: "No." He (peace and blessings be upon him) said: "Tell him." The narrator says: Then I met that man and told him, and he said: "May the One for whose sake you loved me love you." Imam al-Hakim said that the chain of this hadith is sahih (authentic), but Imam Bukhari and Imam Muslim did not record it. And its supporting narration (shahid) is this hadith of Sayyiduna al-Miqdam bin Ma'dikarib (may Allah be pleased with him):

It is narrated from Sayyiduna al-Miqdam bin Ma'dikarib (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "When one of you loves his brother, let him inform him of it."

It is narrated from Sayyiduna Anas (may Allah be pleased with him) that he said: The Messenger of Allah (peace and blessings be upon him) said: "Whenever two men love one another for the pleasure of Allah Almighty, the better of the two is the one whose love for his companion is more intense." Imam al-Hakim said that the chain of this hadith is sahih (authentic), but Imam Bukhari and Imam Muslim did not record it.