RECIPROCAL LOVE H 386 "A Companion was with the Prophet, praise and peace be upon him, when a man passed and the former said: 'O Messenger of Allah, praise and peace be upon him, I love that person.' The Prophet, praise and peace be upon him, asked: 'Have you told him?' He replied: 'No.' The Prophet, praise and peace be upon him, said: 'Tell him.' So he went up to the man and told him: 'I love you for the Sake of Allah.' The other replied: 'May Allah, for whose Sake you love me, love you.'" R 386 Abu Daud with a chain up to Anas who related this.
385- وعن أنس رضي الله عنه : أنَّ رَجُلاً كَانَ عِنْدَ النَّبيِّ ، صلى الله عليه وآله وسلم ، فَمَرَّ رَجُلٌ بِهِ ، فَقَالَ : يَا رَسُول الله ، أنِّي لأُحِبُّ هَذَا ، فَقَالَ لَهُ النَّبيّ صلى الله عليه وآله وسلم : "أأعْلَمْتَهُ ؟" قَالَ : لا . قَالَ : "أعْلِمْهُ" فَلَحِقَهُ ، فَقَالَ : إنِّي أُحِبُّكَ في الله ، فَقَالَ : أَحَبَّكَ الَّذِي أحْبَبْتَنِي لَهُ . رواه أَبُو داود بإسناد صحيح .