Kitāb al-Zuhd
Hadith 174محمد بن سنان عن يزيد بن خليفة قال: سمعت أبا عبد الله عليه السلام يقول: من عمل لله كان ثوابه على الله ومن عمل للناس كان ثوابه على الناس ان كل رياء شرك
8.Muḥammad ibn Sinān narrated from Yazīd ibn Khalīfah who said, “I heard Abā ʿAbdillāh (a) say, ‘Whoever does a deed for [the sake of] Allah, his reward is upon Allah, and whoever does a deed for [praise from] the people, his reward is upon the people. Verily every act done to show off is [a form of] polytheism.’”