And Allah would not let a people stray after He has guided (9:115)

Almuntakhab Fi Tafsir Alquran Alkarim

Nor would Allah lead, people into error after He has guided them lo His path of righteousness until He has explicitly made known to them what they must avoid and they did not, Allah is indeed Alimun (Omniscient) of all in all

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(9:115) It is not the way of Allah to let people go astray after He has given them guidance, until He makes plain to them all that they should avoid *114 : surely Allah has the knowledge of everything.

And Allah would not let a people stray after He has guided meaning

*114) "He makes plain to the people. . . . " beforehand that they should avoid such and such thoughts, deeds and ways. But if they take no heed, and persist in wrong thinking and wrongdoing, Allah withholds His guidance from them and lets them follow the wrong way they themselves choose to follow.
This is the general formula that helps understand those passages of the Qur'an in which Allah ascribes to Himself the guidance and the deviation of the people. Allah's guidance is that He makes plain to them the Right Way through His Prophets and Books. Then He enables those who have the intention, to follow the Right Way. On the other hand, He dces not force and compel them to follow the Right Way, if they themselves intend to persist in the wrong ways in spite of the fact that the Right Way has been made quite clear to them; He rather enables them to follow the way they themselves intend to follow.
As regards the context in which this occurs here, it is plain that it is meant to warn those people who have been mentioned in the preceding passage, and to introduce those who are .going to be mentioned in the succeeding passage
 

And Allah would not let a people stray after He has guided meaning in Urdu

اللہ کا یہ طریقہ نہیں ہے کہ لوگوں کو ہدایت دینے کے بعد پھر گمراہی میں مبتلا کرے جب تک کہ انہیں صاف صاف بتا نہ دے کہ انہیں کن چیزوں سے بچنا چاہیے درحقیقت اللہ ہر چیز کا علم رکھتا ہے