Mishkat al-Masabih 19 Jihad كتاب الجهاد 268

وَعَنِ ابْنِ عُمَرَ قَالَ: رَأَيْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَوَّلُ مَا جَاءَهُ شيءٌ بدَأَ بالمحرَّرينَ. رَوَاهُ أَبُو دَاوُد

Ibn ‘Umar told that he saw the first thing God’s Messenger did immediately anything came to him was to give something to those who had been set free. Abu Dawud transmitted it.