وإن يمسسك الله بضر
And if Allah touches you with harm,
This verse contains the explanation that good, evil, benefit and harm only come from Allah alone and no one shares with His power over these things. Therefore, He is the One Who deserves to be worshipped alone, without ascription of partners
فﻼ كاشف له إﻻ هو وإن يردك بخير فﻼ رآد لفضله يصيب به من يشاء من عباده
there is none who can lift it but He. And if He intends good for you, then none can repel. His favor which He causes to reach whom He wills among His servants.
Concerning His statement,
وهو الغفور الرحيم
And He is the Pardoning, the Merciful.
This means that He is forgiving and merciful towards those who turn to Him in repentance, regardless of what sin the person has committed. Even if the person associated a partner with Allah, verily Allah would forgive him if he repented from it