Tafsir of Al-Hijr 15:64

وأتيناك بالحق

And we have brought you the truth, It is like the Ayah,

ما ننزل المليكة إﻻ بالحق

We do not send the angels down except with the truth. (15:8)

وإنا لصادقون

and certainly, we tell the truth. They said this in affirmation of the news that they brought him, that he would be saved and his people would be destroyed