Allah informs His Messenger, peace be upon him, that among the bedouins around Al-Madinah there are hypocrites and in Al-Madinah itself, those,
مَرَدُواْ عَلَى النَّفَاقِ
(who persist in hypocrisy;) meaning they insisted on hypocrisy and continued in it Allah's statement,
لاَ تَعْلَمُهُمْ نَحْنُ نَعْلَمُهُمْ
(you know them not, We know them), does not contradict His other statement,
وَلَوْ نَشَآءُ لأَرَيْنَـكَهُمْ فَلَعَرَفْتَهُم بِسِيمَـهُمْ وَلَتَعْرِفَنَّهُمْ فِى لَحْنِ الْقَوْلِ
(Had We willed, We could have shown them to you, and you should have known them by their marks; but surely, you will know them by the tone of their speech!)47:30, because the latter Ayah describes them by their characteristics, not that the Messenger ﷺ knows all those who have doubts and hypocrisy. The Messenger ﷺ knew that some of those who associated with him from the people of Al-Madinah were hypocrites, and he used to see them day and night but did not know who they were exactly. We mentioned before in the explanation of,
وَهَمُّواْ بِمَا لَمْ يَنَالُواْ
(...and they resolved that (plot) which they were unable to carry out...)9:74 that the Prophet informed Hudhayfah of the names of fourteen or fifteen hypocrites. This knowledge is specific in this case, not that the Messenger of Allah ﷺ was informed of all their names, and Allah knows best. `Abdur-Razzaq narrated that Ma`mar said that Qatadah commented on this Ayah 9:101, "What is the matter with some people who claim to have knowledge about other people, saying, `So-and-so is in Paradise and so-and-so is in the Fire.' If you ask any of these people about himself, he would say, `I do not know (if I will end up in Paradise or the Fire)!' Verily, you have more knowledge of yourself than other people. You have assumed a job that even the Prophets before you refrained from assuming. Allah's Prophet Nuh said,
وَمَا عِلْمِى بِمَا كَانُواْ يَعْمَلُونَ
(And what knowledge have I of what they used to do)26:112 Allah's Prophet Shu`ayb said,
بَقِيَّتُ اللَّهِ خَيْرٌ لَّكُمْ إِن كُنتُم مُّؤْمِنِينَ وَمَآ أَنَاْ عَلَيْكُمْ بِحَفِيظٍ
(That which is left by Allah for you (after giving the rights of the people) is better for you, if you are believers. And I am not a guardian over you)11:86, while Allah said to His Prophet ,
لاَ تَعْلَمُهُمْ نَحْنُ نَعْلَمُهُمْ
(you know them not, We know them.)" Mujahid said about Allah's statement,
سَنُعَذِّبُهُم مَّرَّتَيْنِ
(We shall punish them twice), "By killing and capture." In another narration he said, "By hunger and torment in the grave,
ثُمَّ يُرَدُّونَ إِلَى عَذَابٍ عَظِيمٍ
(and thereafter they shall be brought back to a great (horrible) torment.)" `Abdur-Rahman bin Zayd bin Aslam said, "The torment in this life strikes their wealth and offspring," and he recited this Ayah,
فَلاَ تُعْجِبْكَ أَمْوَلُهُمْ وَلاَ أَوْلَـدُهُمْ إِنَّمَا يُرِيدُ اللَّهُ لِيُعَذِّبَهُمْ بِهَا فِي الْحَيَوةِ الدُّنْيَا
(So let not their wealth nor their children amaze you; Allah only wants to punish them with these things in the life of this world.) 9:55 These afflictions torment them, but will bring reward for the believers. As for the torment in the Hereafter, it is in the Fire,
ثُمَّ يُرَدُّونَ إِلَى عَذَابٍ عَظِيمٍ
(and thereafter they shall be brought back to a great (horrible) torment.)