Use of reporting verbs
Reporting verbs are used in reported speech
The most common reporting verbs are say and tell. However, there are a number of other reporting verbs that can be used instead of say or tell to make more efficient (i.e. shorter) statements and questions.
Consider this original statement in direct speech:
'I'm sure that everything will be alright'
If we reported the statement with say, we would get :
He said that he was sure that everything would be alright
This is an acceptable statement in English, if rather long. However, the words I'm sure that... in this sentence can have the function of assuring someone. Therefore, we can use the reporting verb assure
He assured me that everything would be alright
This is a) shorter, and b) makes the function of the sentence absolutely clear.