(248) بَابُ إِذَا أَحَبَّ الرَّجُلُ أَخَاهُ فَلْيُعْلِمْهُ
Al-Miqdam ibn Ma'dikarib reported that the Prophet, may Allah blesshim and grant him peace, said, "When one of you has love for his brother,he should inform him that he loves him."
Reference: Al-Adab Al-Mufrad 542
In-book reference: Book 30, Hadith 5
English translation: Book 30, Hadith 542