Muhammad bin Uqbah, the freed slave of al-Zubayr (may Allah be pleased with him), said: I asked al-Qasim bin Muhammad (may Allah have mercy on him) about a mukatab of mine who had settled with me (for his freedom) for a large sum of money: was zakah due on it? Al-Qasim bin Muhammad (may Allah have mercy on him) said: Abu Bakr al-Siddiq (may Allah be pleased with him) did not take zakah from any wealth until a full year had passed over it. And when Abu Bakr (may Allah be pleased with him) gave people their stipends, he would ask: Do you have any other wealth on which zakah has become due upon you? If he said: Yes, he would take the zakah from his stipend; and if he said: No, he would hand over the whole stipend to him and take nothing at all from it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7354