Al-Kāfi - Volume 2 > Truthfulness and Trust
Hadith #8

8ـ أَبُو عَلِيٍّ الأشْعَرِيُّ عَنْ مُحَمَّدِ بْنِ سَالِمٍ عَنْ أَحْمَدَ بْنِ النَّضْرِ الْخَزَّازِ عَنْ جَدِّهِ الرَّبِيعِ بْنِ سَعْدٍ قَالَ قَالَ لِي أَبُو جَعْفَرٍ (عَلَيهِ السَّلام) يَا رَبِيعُ إِنَّ الرَّجُلَ لَيَصْدُقُ حَتَّى يَكْتُبَهُ الله صِدِّيقاً.

8. Abu Ali al-Ash’ari has narrated from Muhammad ibn Salim from Ahmad ibn al- Nadr al-Khazzaz from his grandfather al-Rabi’ ibn Sa’d who has said the following: “Once abu Ja’far (a.s.) said to me, ‘O Rab’i, a man must keep speaking the truth until Allah writes him down as a truthful one.’”