ʿAbdullāh b. Masʿūd – Allāh be pleased with him – said:

The victim of theft might continue to suspect and conjecture [about who stole from him] until he becomes worse [in sin] than the thief.

Al-Bukhārī, Al-Adab Al-Mufrad no. 1289. Its chain of transmission was graded ṣaḥīḥ by Al-Albānī in Ṣaḥīḥ Al-Adab Al-Mufrad no.974.