Surah Hud Tafseer

وَيَصْنَعُ الْفُلْكَ وَكُلَّمَا مَرَّ عَلَيْهِ مَلٌ مِّن قَوْمِهِ سَخِرُواْ مِنْهُ

And as he was constructing the ship, whenever the chiefs of his people passed by him, they mocked at him.

This means that they teased him and rejected his threat that they would drown (in the forthcoming flood).

قَالَ إِن تَسْخَرُواْ مِنَّا فَإِنَّا نَسْخَرُ مِنكُمْ

He said:"If you mock at us, so do we mock at you likewise...

This is a severe threat and a serious warning.

كَمَا تَسْخَرُونَ