Imam Sufyaan (rahimahullah) once wrote in a letter of advice:

"...Allah (azza wa jal) says:



"And take a provision (with you) for the journey, but the best provision is At-Taqwa (piety, righteouness, etc)."(Qur'an 2:197)



Piety here means staying away from acts of trangression...My brother, fear Allah; be truthful in speech, and make your intentions sincere and pure; perform various kinds of good deeds, deeds that are not full of deceit and duplicity. Verily, Allah sees you even though you do not see Him. He is with you (with His knowledge) wherever you are. There is nothing about you that is hidden from Him. Do not deceive Allah, lest He does the same with you, for if one deceives Allah, Allah deceives him; furthemore, faith (Eemaan) leaves such a person, though he may not be aware of the fact that it has left him.



Do not concoct evil plots against any Muslim, for the evil plot encompasses and harms no one save the one who concocted it. And do not transgress against any Muslim, for Allah (azza wa jal) says:



"O mankind! Your rebellion (disobedience to Allah) is only against your ownselves." (Qur'an 10: 23)



Do not cheat or deceive any believer, for cheating and deceiving a believer means that you have some hypocrisy in your heart. Do not be jealous and do not backbite, for these sins nullify your good deeds. Some jurists would perform ablution after backbiting, just as they would perform ablution after they would release impurities from their bodies.



Improve your secret and private life, and Allah will improve your public and social life. Make matters well between you and Allah, and Allah will make matters well between you and people. Work for the Hereafter, and Allah will be enough for you in your worldly concerns. Purchase the Hereafter, and use this worldly life as a method of payment for your purchase, and as a result, you will gain profit in this world and in the Hereafter. But do not purchase this world at the cost of the Hereafter; for if you do so, you will lose out on both worlds."



Source: Biography of Imam Sufyaan ath-Thawri



May Allah have mercy on him, ameen