Nahj al-Balāgha

Hadith 2126
secrettrustworthiness
١٦٢. وَقَالَ (عليه ‏السلام): مَنْ كَتَمَ سِرَّهُ كَانَتِ الْخِيرَةُ بِيَدِهِ.
162. Amīr al-mu’minīn, peace be upon him, said: He who guards his secrets retains control in his own hands.
Source: al-Sharīf al-Raḍī