Messenger of Allah ﷺ said, "A pious slave gets a double reward." Abu Huraira added: By Him in Whose Hands my soul is but for Jihad (i.e. holy battles), Hajj, and my duty to serve my mother, I would have loved to die as a slave. (Using translation from Bukhārī 2548)
قَالَ رَسُولُ اللهِ ﷺ لِلْعَبْدِ الْمَمْلُوكِ الْمُصْلِحِ أَجْرَانِ وَالَّذِي نَفْسُ أَبِي هُرَيْرَةَ بِيَدِهِ لَوْلَا الْجِهَادُ فِي سَبِيلِ اللهِ وَالْحَجُّ وَبِرُّ أُمِّي لَأَحْبَبْتُ أَنْ أَمُوتَ وَأَنَا مَمْلُوكٌ