Nahj al-Balāgha

Hadith 2158
truthfulness
٢٤٨. وَقَالَ (عليه ‏السلام): مَنْ ظَنَّ بِكَ خَيْراً فَصَدِّقْ ظَنَّهُ.
248. Amīr al-mu’minīn, peace be upon him, said: If a person has a good idea about you make his idea be true.
Source: al-Sharīf al-Raḍī