Yazid bin Khusayfah (may Allah have mercy on him) asked Sulayman bin Yasar (may Allah have mercy on him) about a man who has wealth and owes a debt equal to it: is zakah due from him? He said: No zakah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7614