وَاتَّبِعُوا أَحْسَنَ مَا أُنزِلَ إِلَيْكُم مِّن رَّبِّكُمAnd follow the best of that which is sent down to you from your Lord,means, the Qur'an.مِّن قَبْلِ أَن يَأْتِيَكُمُ العَذَابُ بَغْتَةً وَأَنتُمْ لَا تَشْعُرُونَbefore the torment comes on you suddenly while you perceive not!means, without you realizing it