Being trustworthy is one of the foremost characteristics of the believers. All the messengers have proved their righteousness to their people and been know as trustworthy and decent people. Fulfilling every engagement is a significant part of this trustworthiness.
Believers should keep their promises, and never commit themselves to anything which they think they will not be able to fulfill. It is said in the Qur’an as follows:
“O you who believe, why do you say that which you do not do? Greviously odious is it in the sight of Allah that you say that you do not do.”