Ayah 11:
إنما تنذر من اتبع الذكر وخشي الرحمن بالغيب فبشره بمغفرة وأجر كريم
Innamaa tunziru manit taba 'az-Zikra wa khashiyar Rahmaana bilghaib, fabashshirhu bimaghfiratinw-wa ajrin kareem
You can only warn one who follows the message and fears the Most Merciful unseen. So give him good tidings of forgiveness and noble reward.
One very profound message here is that da'wah is a responsibility from Allaah and it must be discharged. It is not just to benefit the person being invited (mad'u), but also for the inviter (da'i) regardless if someone is listening or not. We do not slacken in our efforts and accept failure. We strive because we are benefiting from this struggle. At the end of the day, the Messenger of Allaah pbuh wanted to see some results, to see some validation, some vindication, to see that what he's doing means something and it brings some change.
Innamaa in this form serves the purpose of restriction and specification, "in actuality, you are only".
Attaba'a az-Zikr | Word Analysis
Az-Zikr points to the Qur'aan as time and time again it has been described as that (54, 40)
ولقد يسرنا القرآن للذكر فهل من مدكر
And We have indeed made the Qur'aan easy to understand and remember...
The fact that it's in its proper form az-Zikr is even more evidence of the fact that it points specifically to the Qur'aan.
So the one who will ittaba' (literally meaning "to follow") the Qur'aan.
What does it mean to follow the Qur'aan?
In other places, we are told (39, 18)
الذين يستمعون القول فيتبعون أحسنه أولئك الذين هداهم الله وأولئك هم أولو الألباب
Who listen to speech (very attentively, carefully) and follow it (in its most excellent fashion). Those are the ones Allaah has guided and those are people of understanding.
Thus, following the Qur'aan means to listen, understand it, internalize it, act upon it, and even spend themselves in further spreading it. This is the real following of the Qur'aan. This is the person whom the Messenger of Allaah pbuh is warning.
Khashiya ar-Rahman | Word Analysis
But that's not all. This person has a second quality as well. Khashiya he fears, is overwhelmed by ar-Rahman. This is an interesting combination, to fear the Most Merciful.
Why not say Allaah?
By saying Ar-Rahman the reader or listener thinks of all the blessings in his life and feels a sense of obligation to turn to and worship Allaah. The title, relationship, status is mentioned to make one feel a sense of obligation. He has blessed you with everything you have.
Also, by mentioning Ar-Rahman it's His right upon us to be worshipped and for us to fear disappointing Him. There is no contradiction.
