Abu Ammar said: We asked Sayyiduna Qays bin Sa'd bin Ubadah (may Allah be pleased with him) about Sadaqat al-Fitr, and he said: The Messenger of Allah (peace and blessings be upon him) ordered us to give it before zakah was revealed; then after that he neither ordered us to give it nor forbade us from it, so we kept giving it.
Hadith Referenceالمعجم الكبير للطبراني / باب القاف / 15977