وَمِنَ النَّاسِ مَن يَعْبُدُ اللَّـهَ عَلَىٰ حَرْفٍ ۖ فَإِنْ أَصَابَهُ خَيْرٌ اطْمَأَنَّ بِهِ ۖ وَإِنْ أَصَابَتْهُ فِتْنَةٌ انقَلَبَ عَلَىٰ وَجْهِهِ خَسِرَ الدُّنْيَا وَالْآخِرَةَ ۚ ذَٰلِكَ هُوَ الْخُسْرَانُ الْمُبِينُ

  “And among mankind is he who worships Allaah as it were upon the edge (i.e. in doubt): if good befalls him, he is content therewith; but if a trial befalls him he turns back on his face (i.e. reverts to disbelief after embracing Islam). He loses both this world and the Hereafter. That is the evident loss” 

Quran, [al-Hajj 22:11]