The blame is on those who ask your permission to stay behind, even though they have no excuse. They have chosen to be with the sedentary. Consequently, God has sealed their hearts, and thus, they do not attain any knowledge.
إِنَّمَا السَّبيلُ عَلَى الَّذينَ يَستَـٔذِنونَكَ وَهُم أَغنِياءُ رَضوا بِأَن يَكونوا مَعَ الخَوالِفِ وَطَبَعَ اللَّهُ عَلىٰ قُلوبِهِم فَهُم لا يَعلَمونَ
innamas sabeelu ‘alal lazeena yasta’zinoonaka wa hum aghniyaaa’; radoo biany-yakoonoo ma’al khawaalifi wa taba’al laahu ‘alaa quloobihim fahum laa ya’lamoon