Mishkat al-Masabih 14 Emancipation كتاب العتق 4

وَعَن عَمْرو بن عبسة أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «مَنْ بَنَى مَسْجِدًا لِيُذْكَرَ اللَّهُ فِيهِ بُنِيَ لَهُ بَيْتٌ فِي الْجَنَّةِ وَمَنْ أَعْتَقَ نَفْسًا مُسْلِمَةً كَانَتْ فِدْيَتَهُ مِنْ جَهَنَّمَ. وَمَنْ شَابَ شَيْبَةً فِي سَبِيلِ اللَّهِ كَانَتْ لَهُ نُورًا يَوْم الْقِيَامَة» . رَوَاهُ فِي شرح السّنة

‘Amr b. ‘Abasa reported the Prophet as saying, “If anyone builds a mosque that God may be mentioned in it, a house will be built for him in paradise; if anyone emancipates a Muslim, that will be his ransom from jahannam; if anyone develops a grey hair while in ‘God’s path, it will be a light for him on the day of resurrection.” It is transmitted in Sharh as-sunna .