Verse 3: When Allah (swt) addresses His believers, He gives them examples of those who came before them. Do you think that only you are suffering and that the people who came before you had an easy time? Some of the muffasireen (commentators) have mentioned that this verse is referring to the tribulations of Ammar ibn Yasir. The believers were suffering and some of them considered leaving Islam. They were told to look at those who came before, like Ammar. He lost his parents - they were both martyred; the first martyrs of Islam, Sumayya and Yasir.  May Allah be pleased with them. 
Verse 4: Do they think that if they do something evil, they can 
outmaneuver (run away from) Us? Evil is the judgement that they make. Imam ‘Ali (a) is reported to have said, “The parts of your body are the army of Allah.” Your body is working for Allah, Your eyes and ears are His witnesses, they will bear testimony. Human beings 
cannot escape if they sin. 
Verse 5: Whoever hopes to meet Allah, the term appointed by Allah will then most surely come, and He is the Hearing, the Knowing.