Narrated Zaid bin Thabit: When we collected the fragmentary manuscripts of the Qur'an into copies, I missed one of the Verses of Surat al-Ahzab which I used to hear Allah's Messenger ﷺ reading. Finally I did not find it with anybody except Khuza'ima Al-Ansari, whose witness was considered by Allah's Messenger ﷺ equal to the witness of two men. (And that Verse was:) 'Among the believers are men who have been true to their covenant with Allah'.
This hadith teaches us that we should be honest and sincere in our dealings especially when making a promise or agreement with someone else or even more so when making a promise or agreement with God Almighty Himself as He knows all our intentions and will reward us accordingly for keeping up our end of any bargain we make Him. We should also strive for justice, fairness, truthfulness, loyalty, integrity and trustworthiness in all aspects of life so that we can be counted among those who are true believers according to this verse from Surat al-Ahzab mentioned in this hadith.