"God would not leave the believers in that state in which you are, until He separates the wicked from the good." This means: until He distinguishes the believers from the hypocrites on the day of Uhud; according to the interpretation of Qatada.
"Nor would God inform you of the unseen." The hypocrites said: "What is the matter with Muhammad? If he is truthful, why does he not inform us of who will believe before they believe?" So God said: "Nor would God inform you of the unseen, but God chooses of His messengers whom He wills," meaning He selects from among His messengers whom He wills, and informs them of what He wills (of the unseen).
﴿مَا كَانَ اللَّهُ لِيَذَرَ الْمُؤْمِنِينَ عَلَى مَا أَنْتُمْ عَلَيْهِ حَتَّى يُمَيّز﴾ أَي: يعْزل ﴿الْخَبِيثَ مِنَ الطَّيِّبِ﴾ ميز الْمُؤمنِينَ من الْمُنَافِقين يَوْم أحد؛ فِي تَفْسِير قَتَادَة. ﴿وَمَا كَانَ اللَّهُ لِيُطْلِعَكُمْ عَلَى الْغَيْبِ﴾ قَالَ المُنَافِقُونَ: مَا شَأْن مُحَمَّد؛ إِن كَانَ صَادِقا لَا يخبرنا بِمن يُؤمن بِهِ قبل أَن يُؤمن؟ فَقَالَ الله: ﴿وَمَا كَانَ اللَّهُ لِيُطْلِعَكُمْ عَلَى الْغَيْبِ وَلَكِنَّ الله يجتبي﴾ أَي: يستخلص ﴿مِنْ رُسُلِهِ مَنْ يَشَاء﴾ فيطلعه على مَا يَشَاء (من الْغَيْب).
