Truth came, and the messengers said it plainly.
We have brought the truth, and we are truthful
Ibn Kathir links this to 15:8: We do not send the angels down except with the truth. Earlier in this surah, Makkah had demanded angels as proof. Here is what angels look like when they come: a decree, not a show.
You keep asking for a sign before you change: a dream, a miracle, a perfect moment. When the real sign comes, it comes with consequences already attached. It is kinder to act on the message you already have.
If Allah wanted me to change, He would send me a clear sign.
The signs I already have are mercy; a final sign arrives carrying the outcome.
Act today on one piece of guidance you already know, without waiting for a sign.