Sayyiduna Ibn Umar (may Allah be pleased with them both) relates: I was sitting with the Prophet (peace and blessings be upon him) when a man came, greeted him (peace and blessings be upon him) with salam, then went away. I said: O Messenger of Allah! By Allah, I love this man. He (peace and blessings be upon him) said: "Have you told him?" I said: No. He (peace and blessings be upon him) said: "Then tell your brother." So I went to him, greeted him with salam, and placing my hand on his shoulder I said: By Allah, I love you for the sake of Allah. He said: And I too love you for the sake of Allah. And I said: Had the Prophet (peace and blessings be upon him) not commanded me to tell you, I would not have done so.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13304