It is narrated from Sayyiduna Miqdam bin Ma'dikarib (may Allah be pleased with him), and he witnessed the time of the Prophet (peace and blessings of Allah be upon him), that the Prophet (peace and blessings of Allah be upon him) said: "When one of you loves his brother, he should inform him that he loves him."
Hadith Referenceالادب المفرد / كتاب / 542
Hadith Gradingالألبانی:صحيح
Hadith Takhrij«صحيح : أخرجه أبوداؤد ، كتاب الأدب ، باب الرجل يحب الرجل على خير يراه : 5124 و الترمذي : 2392 و النسائي فى الكبرىٰ : 9963 - انظر الصحيحة : 2515»