Ibn al-Yaman reported: Sufyan al-Thawri, may Allah have mercy on him, said, “Religious innovations are more beloved to Satan than sinful disobedience to Allah. Disobedience is repented from, but innovations are not repented from.”
Source: Ḥilyat al-Awliyā’ 7/26
عن ابْن يَمَانٍ وَعَنْ سُفْيَانَ الثَّوْرِيِّ رَحْمَةُ اللَّهِ تَعَالَى عَلَيْهِ أَنَّهُ قَالَ الْبِدْعَةُ أَحَبُّ إِلَى إِبْلِيسَ مِنَ الْمَعْصِيَةِ الْمَعْصِيَةُ يُتَابُ مِنْهَا وَالْبِدْعَةُ لَا يُتَابُ مِنْهَا
7/26 حلية الأولياء وطبقات الأصفياء