Allah said,

﴿وَإِذَا جَآءُوكُمْ قَالُواْ ءَامَنَّا وَقَدْ دَّخَلُواْ بِالْكُفْرِ وَهُمْ قَدْ خَرَجُواْ بِهِ﴾

(When they come to you, they say, "We believe.'' But in fact they enter with (an intention of) disbelief and they go out with the same.) This is the description of the hypocrites, for they pretend to be believers while their hearts hide Kufr. So Allah said;

﴿وَقَدْ دَّخَلُواْ﴾

(But in fact they enter) on you, O Muhammad,

﴿بِالْكُفْرِ﴾

(with disbelief) in their hearts and they depart with Kufr, and this is why they do not benefit from the knowledge they hear from you, nor does the advice and reminder move them. So,

﴿وَهُمْ قَدْ خَرَجُواْ بِهِ﴾

(and they go out with the same) meaning, they alone,

﴿وَاللَّهُ أَعْلَمُ بِمَا كَانُواْ يَكْتُمُونَ﴾

(and Allah knows all that they were hiding.) Allah knows their secrets and what their hearts conceal, even if they pretend otherwise with His creatures, thus pretending to be what they are not. Allah, Who has perfect knowledge of the seen and unseen, has more knowledge about the hypocrites than any of His creatures do and He will recompense them accordingly. Allah's statement,

﴿وَتَرَى كَثِيراً مِّنْهُمْ يُسَـرِعُونَ فِى الإِثْمِ وَالْعُدْوَانِ وَأَكْلِهِمُ السُّحْتَ﴾

(And you see many of them (Jews) hurrying for sin and transgression, and eating illegal things.) They hurry to devour prohibited and illegal things, all the while transgressing against people, unjustly consuming their property through bribes and Riba,

﴿لَبِئْسَ مَا كَانُواْ يَعْمَلُونَ﴾

(Evil indeed is that which they have been doing.) Indeed, horrible is that which they used to do and the transgression that they committed.