Narrated Al-Miqdam ibn Ma’dikarib:
The Prophet (ﷺ) said: ‘When a man loves his brother, he should tell him that he loves him.’
«إذا أحب أحدكم أخاه فليعلمه أنه يحبه» .
(صحيح) … [حم خد د ت حب ك] عن المقداد بن معدي كرب [حب] عن أنس [خد] عن رجل من الصحابة. الصحيحة 418, 2515.
This hadith was narrated by Ahmad 4/130, al-Bukhari in al-Adabul-mufrad 542, at-Tirmidhi 2392, Ibn Hibban 570 and al-Hakim 4/189 from the words of al-Mikadam ibn Ma’dikarib; Ibn Hibban from the words of Anas; al-Bukhari in “al-Adabul-mufrad” from the words of one of the companions of the Prophet (peace and blessings of Allah be upon him).
Sheikh al-Albani called the hadith authentic. See Saheeh al-jami ‘as-sagyir 279. Similar hadith in Abu Dawood 5125.