|Shirk is the Worst form of Wrong, its Practitioner shall never succeed. Allah threatens those who as|
﴿لاَ بُرْهَانَ لَهُ﴾
(of whom he has no proof), meaning no evidence for what he says. Then Allah says:
﴿وَمَن يَدْعُ مَعَ اللَّهِ إِلَـهَا ءَاخَرَ لاَ بُرْهَانَ لَهُ بِهِ﴾
(And whoever invokes, besides Allah, any other god, of whom he has no proof;) this is a conditional sentence, whose fulfilling clause is:
﴿فَإِنَّمَا حِسَابُهُ عِندَ رَبِّهِ﴾
(then his reckoning is only with his Lord.) meaning, Allah will call him to account for that. Then Allah tells us:
﴿إِنَّهُ لاَ يُفْلِحُ الْكَـفِرُونَ﴾
(Surely, disbelievers will not be successful.) meaning, they will not be successful with Him on the Day of Resurrection; they will not prosper or be saved.
﴿وَقُل رَّبِّ اغْفِرْ وَارْحَمْ وَأنتَ خَيْرُ الرَحِمِينَ ﴾
(And say: "My Lord! Forgive and have mercy, for You are the best of those who show mercy!'') Here Allah is teaching us to recite this supplication, for forgiveness, in a general sense, means wiping away sins and concealing them from people, and mercy means guiding a person and helping him to say and do good things.