﴿ وَمِنَ ٱلنَّاسِ مَن يَقُولُ ءَامَنَّا بِٱللَّهِ فَإِذَآ أُوذِىَ فِى ٱللَّهِ جَعَلَ فِتْنَةَ ٱلنَّاسِ كَعَذَابِ ٱللَّهِ وَلَئِن جَآءَ نَصْرٌۭ مِّن رَّبِّكَ لَيَقُولُنَّ إِنَّا كُنَّا مَعَكُمْ ۚ أَوَلَيْسَ ٱللَّهُ بِأَعْلَمَ بِمَا فِى صُدُورِ ٱلْعَٰلَمِينَ ﴾

“Now there is among men many a one who says [of himself and of others like him], “We do believe in God” - but whenever he is made to suffer in God’s cause, he thinks that persecution at the hands of man is as [much to be feared, or even more than,] God’s chastisement; whereas, if succour from thy Sustainer comes [to those who truly believe] he is sure to say. “Behold, we have always been with you!” Is not God fully aware of what is in the hearts of all creatures?”

(1)-It means that such people join the infidels when they apprehend some kind of torture from them, but when Allah's help will come to the Muslims in a battle against the infidels, they will pretend to be Muslims on the plea that they had joined the infidels only because they feared to be persecuted by them. (2)-The sense is that they did not believe in Islam with their hearts, and this fact cannot: be concealed from Him, because He knows whatever lies in the hearts of the people.