Word by Word Analysis

وَإِذَا لَمْ تَأْتِهِم بِـَٔايَةٍ قَالُوا۟ لَوْلَا ٱجْتَبَيْتَهَا ۚ قُلْ إِنَّمَآ أَتَّبِعُ مَا يُوحَىٰٓ إِلَىَّ مِن رَّبِّى ۚ هَـٰذَا بَصَآئِرُ مِن رَّبِّكُمْ وَهُدًى وَرَحْمَةٌ لِّقَوْمٍ يُؤْمِنُونَ 203

And when you, [O Muḥammad], do not bring them a sign [i.e., miracle], they say, "Why have you not contrived it?" Say, "I only follow what is revealed to me from my Lord. This [Qur’ān] is enlightenment from your Lord and guidance and mercy for a people who believe."