Sufyan on Honesty: You must be truthful in everything you do

Abu Nu’aym reported: Sufyan al-Thawri, may Allah have mercy on him, said, “You must be honest in all things. Beware of lying and treachery and sitting with those who commit them; it will all be a burden of sin. Beware, my brother, of ostentation in words and deeds, as it is a form of idolatry. Beware of vanity, for good deeds within which is vanity will not be exalted.”

Source: Ḥilyat al-Awliyā’ 7/82

عن أبي النعيم قال سفيان الثوري رحمه الله عَلَيْكَ بِالصِّدْقِ فِي الْمَوَاطِنِ كُلِّهَا وَإِيَّاكَ وَالْكَذِبَ وَالْخِيَانَةَ وَمُجَالَسَةَ أَصْحَابِهَا فَإِنَّهَا وِزْرٌ كُلُّهُ وَإِيَّاكَ يَا أَخِي وَالرِّيَاءَ فِي الْقَوْلِ وَالْعَمَلِ فَإِنَّهُ شِرْكٌ بِعَيْنِهِ وَإِيَّاكَ وَالْعُجْبَ فَإِنَّ الْعَمَلَ الصَّالِحَ لَا يُرْفَعُ وَفِيهِ عُجْبٌ

7/82 حلية الأولياء وطبقات الأصفياء