ولين أذقناه رحمة منا من بعد ضراء مسته ليقولن هذا لي
And truly, if We give him a taste of mercy from Us, after some adversity has touched him, he is sure to say: "This is due to my (merit)...''
means, if something good happens to him or some provision comes to him after a period of difficulty, he says, `this is because of me, because I deserve this from my Lord.'
وما أظن الساعة قايمة
I think not that the Hour will be established.
means, he does not believe that the Hour will come. So when he is given some blessing, he becomes careless, arrogant and ungrateful, as Allah says:
كﻼ إن اﻻنسن ليطغى
أن رءاه استغنى
Nay! Verily, man does transgress. Because he considers himself self-sufficient. (96:6-7)
ولين رجعت إلى ربي إن لي عنده للحسنى
But if I am brought back to my Lord, surely there will be for me the best with Him.
means, `if there is a Hereafter after all, then my Lord will be generous and kind to me just as He was in this world.' So he expects Allah to do him favors in spite of his bad deeds and lack of certain faith.
Allah says:
فلننبين الذين كفروا بما عملوا ولنذيقنهم من عذاب غليظ
Then, We verily will show to the disbelievers what they have done, and We shall make them taste a severe torment.
Thus Allah threatens punishment and vengeance to those whose conduct and belief is like that