al-Lyth bin Abi Sulaym الليث بن أبي سليم · Chapters on Tafsir

that 'Umar bin Al-Khattab was asked about this Ayah: And when your Lord brought forth from the Children of Adam, from their loins, their seed and made them testify as to themselves: "Am I not your Lord?" They said: "Yes! We testify," lest you should say on the Day of Resurrection: 'Verily, we have been unaware of this (7:172).'" So 'Umar bin Al-Khattab said: "I heard the Messenger of Allah (ﷺ) being asked about it. So the Messenger of Allah…

the Messenger of Allah said: “Verily, when the slave (of Allah) commits a sin, a black spot appears on his heart. When he refrains from it, seeks forgiveness and repents, his heart is polished clean. But if he returns, it increases until it covers his entire heart. And that is the ‘Ran’ which Allah mentioned: ‘Nay, but on their hearts is the Ran which they used to earn.’”