مُسْنَدُ أَحْمَدَ
Musnad Ahmad 4000
Musnad of Abdullah bin Mas'ood
It was narrated that 'Abdullah - he (i.e. Shareek) narrated it to us as a marfoo’ report the first time, then he stopped narrating it as marfoo’- said: "Even if riba increases, it will ultimately lead to less.”
Musnad Ahmad 4026A saheeh hadeeth]