مَا نُنَزِّلُ ٱلۡمَلَٰٓئِكَةَ إِلَّا بِٱلۡحَقِّ وَمَا كَانُوٓاْ إِذٗا مُّنظَرِينَ ٨
We do not send down the angels except with truth;1 and they [i.e., the disbelievers] would not then be reprieved.
Translation: Saheeh International (English)
1 i.e., with a message or, as the conclusion of the verse suggests, to carry out a promised punishment.
Each word's meaning and sound
In response to their idea of having the angels brought forth, Allah said: I will not send the angels except when it becomes wise to do so, that is, when your time comes to be penalised. And if the angels were sent and they did not believe, then their punishment would become imminent.
Al-Mukhtasar in interpreting the Noble Quran