Zayd bin Aslam (may Allah have mercy on him) said: In the era of Ignorance, a man would have a debt owed to him by another man for a fixed term. When the term expired, the lender would say: Will you pay, or will you give usury? If he paid, he would take it; otherwise he would increase what was owed by him, and the other would extend the term.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10467