The Prophet ﷺ said:
اسْتَفْتِ نَفْسَكَ اسْتَفْتِ قَلْبَكَ الْبِرُّ مَا اطْمَأَنَّتْ إِلَيْهِ النَّفْسُ وَاطْمَأَنَّ إِلَيْهِ الْقَلْبُ وَالْإِثْمُ مَا حَاكَ فِي النَّفْسِ وَتَرَدَّدَ فِي الصَّدْرِ وَإِنْ أَفْتَاكَ النَّاسُ وَأَفْتَوْكَ
Consult your soul, consult your heart. Righteousness is what reassures your soul and your heart, and sin is what wavers in your soul and puts tension in your chest, even if the people approve it in their judgments again and again.
Sunan al-Dārimī 2575, Grade: Sahih