This is addressed in the second person to the Prophet ﷺ.
عَجِبۡتُ
ʿajibtu
“I am amazed while they mock”
This is in the first person, ascribing this verb (with appropriate meaning) to Allah.
Explanation
These readings give rise to various interpretations. The first reading remarks on how the Prophet ﷺ reacts (or should react) to the mockery he faced. The second is understood in line with several hadiths which also ascribe 'amazement' (ʿajab) to Allah. It is an expression for how serious this matter is to Him, and the word may be used specifically for the irony that those people found the message 'amazing' in the sense of being too hard to believe [Ibn 'Ashur].
He has revealed to you ˹O Prophet˺ the Book in truth, confirming what came before it, as He revealed the Torah and the Gospel
Explanation
These readings give rise to various interpretations. The first reading remarks on how the Prophet ﷺ reacts (or should react) to the mockery he faced. The second is understood in line with several hadiths which also ascribe 'amazement' (ʿajab) to Allah. It is an expression for how serious this matter is to Him, and the word may be used specifically for the irony that those people found the message 'amazing' in the sense of being too hard to believe [Ibn 'Ashur].