Sayyiduna Qays bin Sa'd bin Ubadah (may Allah be pleased with him) said: We were ordered to fast the day of Ashura; this was before Ramadan was revealed. Then when Ramadan was revealed, we were neither ordered to fast it nor forbidden from it, and we kept fasting it. And we were ordered to give half a sa' per person, whether free or slave, young or old, male or female; then when zakah was revealed, we were neither ordered to give it nor forbidden from it, and we kept giving it.
Hadith Referenceالمعجم الكبير للطبراني / باب القاف / 15979