Al-Miqdam bin Ma’dikarib narrated that the Messenger of Allah (s.a.w) said:
“When one of you loves his brother,then let him inform him of it.”
Reference : Jami` at-Tirmidhi 2392
In-book reference : Book 36, Hadith 89
English translation : Vol.
4, Book 10, Hadith 2392
Al-Manaawi (may Allaah have mercy on him) said:
“Let him tell him that he loves him for the sake of Allaah” means, it is mustahabb for him to tell him, by saying I love you for the sake of Allaah, i.e., not for any other reason such as kindness and so on, because it ensures that the bond will last longer and makes love stronger,
and it increases and multiplies love, and brings people together, thus the Muslims will be united, and troubles and grudges will be dispelled. This is one of the good features of Islam. End quote.
Fayd al-Qadeer (1/319).