كَانُوا مُخْبِرِينَ، مُبَلِّغِينَ عَنِ اللَّهِ تَعَالَى، صَادِقِينَ نَاصِحِينَ لِلْخَلْقِ
They communicated God's message truthfully and sincerely for the good of creation.
Acceptance of prophetic information rests on the messenger's truthfulness. If a prophet could deliberately alter revelation or falsely attribute a command to God, the purpose of messengership—trustworthy guidance—would fail.
Prophetic sincerity means calling people toward truth and salvation. It does not mean every hearer must accept the call. Faithful delivery of the message and the audience's response are distinct matters.