21-41
And messengers before you were mocked at, then that which they used to mock at, surrounded those of them who ridiculed. (R3)
Infidels were surrounded with punishment which they used to laugh at. Such punishment can come any time and no one will be able to help against it.
21-45
Say, “”I warn you only according to the communication (I receive), but the deaf do not hear the call when they are warned.””
The deaf are heedless of the warning. They will realize this injustice they did to themselves when they experience the punishment. On the day of resurrection everyone will be paid exactly according to his account of deeds.
21-48
And We gave to Musa and Harun that which differentiates (between right and wrong) and a light and a reminder for those who guard (against evil),
Like the Torah given to Musa and Harun (PBT) the Quran was revealed to Prophet Muhammed (PBH), therefore the Quran too, should be accepted as a Divine revelation.
21-51
And earlier We gave Ibrahim (instructions to follow) the way (which was) right for him and We knew about him
For details of Ibrahim (PBH) see Commentary Chapter: 19 Verses 41-50 page No 414