وَعَنْ أَسْمَاءَ بِنْتِ أَبِي بَكْرٍ رَضِيَ اللَّهُ عَنْهُمَا قَالَتْ: لَقَدْ أَمَرَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ بِالْعَتَاقَةِ فِي كُسُوفِ الشَّمْسِ. رَوَاهُ البُخَارِيّ

Asma’ daughter of Abu Bakr said that during a solar eclipse the Prophet gave command that slaves should be set free. Bukhari transmitted it.