Musannaf Ibn Abi Shayba 22:251

Ibn ‘Ulayyah narrated to us, from Ayyub, from Abu Qilabah, that people from the people of Kufa came to Abu al-Darda’ and said: "Indeed, brothers from the people of Kufa send you greetings of peace and command you to advise them." He said: "Convey my greetings of peace to them, and command them to give the Qur’an its constraints (khaza’im), for it carries them toward moderation and ease, and keeps them away from injustice and harshness."