Nafi' (may Allah have mercy on him) narrates from Ibn Umar (may Allah be pleased with him) that he said: "Zakat is not obligatory on wealth until a year has passed over it."
Hadith Referenceمسند الإمام الشافعي / كتاب الزكاة / 691
Hadith Takhrijاسناده صحیح اخرجه الترمذى الزكاة، باب ماجاء لازكاة على المال...... الخ (632) ۔ ومالك في المؤطا، الزكاة، باب الزكاة في العين من الذهب والورق والبيهقي : 4 / 103 ، 10 ، 109 ۔ والدارقطني: (2/ 92)۔
It is narrated from Sa’ib bin Yazid (may Allah be pleased with him) that Uthman bin Affan (may Allah be pleased with him) used to say: "This is the month of your zakat; whoever has a debt should pay it off so that only your pure wealth remains, then pay zakat from that."
Hadith Referenceمسند الإمام الشافعي / كتاب الزكاة / 692
Hadith Takhrijاسناده صحيح : اخرجه البيهقي : 4 / 148 ۔ وفى المعرفة السنن والآثار له (2369)- وعبدالرزاق (7086) ۔ و ابن ابي شيبة (1055)۔
Qudamah (may Allah be pleased with him) says: When I used to come to Uthman bin Affan (may Allah be pleased with him) to receive my salary, he would ask me: "Is zakat obligatory on the wealth you possess?" If I said yes, he would deduct zakat from my salary, and if I said no, he would give me my salary.
Hadith Referenceمسند الإمام الشافعي / كتاب الزكاة / 693
Hadith Takhrijاسناده صحيح : اخرجه البيهقي في المعرفة السنن والآثار (2276) ۔ وعبدالرزاق (7029)۔