Abu Ubayd (may Allah have mercy on him) said: By «li-yawmihima» (for their day) is meant the Day of Resurrection, the day for which he freed the sa'ibah and gave the charity; that is, he should not return to benefit from either of them again in this world. It is like a man who frees his slave as a sa'ibah, then the freed man dies and leaves wealth with no heir except the one who freed him. He says: He should not take anything from his inheritance, nor take anything from the sa'ibah's inheritance, except to spend it on people like him. The same is narrated from Ibn Umar (may Allah be pleased with them both), and this practice of theirs was by way of virtue and reward, not because it is forbidden.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الولاء / 21484