Anas reported: The Prophet, peace and blessings be upon him, said, “No Muslim servant visits his brother for the sake of Allah but that a caller from the heavens announces: You are purified and Paradise is purified for you! Otherwise, Allah says in the realms of His throne: My servant has visited Me and his guest for My sake, so I am not pleased for him to have any reward other than Paradise.”
Source: Musnad al-Bazzār 6466
Grade: Hasan li ghayrihi (fair due to external evidence) according to Al-Albani
عَن أَنَس عَن النَّبِيّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ مَا مِنْ عَبْدٍ مُسْلِمٍ أَتَى أَخًا لَهُ يَزُورُهُ فِي اللَّهِ إلاَّ نَادَاهُ مُنَادٍ مِنَ السَّمَاءِ أَنْ طِبْتَ وَطَابَتْ لَكَ الْجَنَّةُ وَإِلَّا قَالَ اللَّهُ فِي مَلَكُوتِ عَرْشِهِ عَبْدِي زَارَ فِيَّ وَعَلَيَّ قِرَاهُ فَلَمْ يَرْضَ اللَّهُ لَهُ بِثَوَابٍ دُونَ الْجَنَّةِ
6466 مسند البزار
2850 المحدث الألباني خلاصة حكم المحدث حسن لغيره في صحيح الترغيب