وَقَالَ فِرْعَوْنُ يَٰهَٰمَٰنُ ٱبْنِ لِى صَرْحًا لَّعَلِّىٓ أَبْلُغُ ٱلْأَسْبَٰبَ · أَسْبَٰبَ ٱلسَّمَٰوَٰتِ فَأَطَّلِعَ إِلَىٰٓ إِلَٰهِ مُوسَىٰ
"Pharaoh said: 'O Hāmān! Build me a lofty tower, that I may reach the ways — the ways of the heavens — and look upon the god of Moses.'"
صَرْح — root ص-ر-ح: to be open, unmixed (ṣarīḥ — plain speech). The word is used of a building that is tall and stands out in the open. The root occurs here for the first time in this series.
أَسْبَاب — singular sabab: a rope, a cable; the tie that lets one reach a place. The "rope" sense of the root was treated at al-Baqara 2/166 (wa taqaṭṭaʿat bihimu'l-asbāb — the snapping of the ties).
The structure of the request is worth recording, and I give it as my own reading: Pharaoh wants to test what Moses says on his own plane — by going up high. That is, he does not reject the claim; he turns it into a problem of architecture.
And the verse gives the outcome of this in a single sentence: wa kadhālika zuyyina li-Firʿawna sūʾu ʿamalih — "thus was his evil deed made to seem fair to him." The verb is passive; the one who made it seem fair is not named.