Musa bin Uqbah (may Allah have mercy on him) narrates from Nafi' (may Allah have mercy on him) that Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) used to pay sadaqat al-fitr on behalf of every slave of his who was on his land or elsewhere, and on behalf of every person under his care, whether young or old, and he would also pay it on behalf of his wife's slaves.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7681