And when it is said to them, "Prostrate to the Most Merciful," (25:60)

Almuntakhab Fi Tafsir Alquran Alkarim

And when they -the infidels- are asked to prostrate their reason to divine revelation and to Him AL-Rahman, they insolently and defiantly ask: Who is AL- Rahman! Shall we prostrate in reverence and submission to an object of worship just because you enjoin us to do so. Their statement accords with their actions They withdraw further and their mental attitude is an incitement to their aversion

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(25:60) When it is said to them. "Prostrate yourselves before the Merciful," they retort, "What is the Merciful? Would you have us prostrate ourselves before whomsoever you will?" *73 And this invitation only helps to increase their hatred all the more. *74

And when it is said to them, "Prostrate to the Most Merciful," meaning

*73) This they said due to their arrogance and stubbornness just as Pharaoh had said to Prophet Moses: "What is the Lord of the universe?" For the disbelievers of Makkah were not unaware of the Merciful (Rahman), nor was Pharaoh unaware of the "Lord of the universe". The wording of the verse itself chows that their question about the "Merciful" was not the result of their ignorance of Him but was due to their rebelliousness; otherwise Allah would not have punished them for this but would have informed them politely that He Himself is "Merciful". Besides this, it is well known istorically that the word Rahman (Merciful) for Allah had been in common usage in Arabia since the ancient times. Please see also E.N. 5 of As-Sajdah and E.N. 35 of Saba.
*74) All scholars are agreed that here a `Prostration of Recital' (Sajdah Talawat) has been enjoined, which means that every reader and every hearer must prostrate himself on reciting or hearing the recital of this verse. According to traditions, the one who hears this verse being recited should say: Zadan Allahu, khudu an-anima zada, lil-a`daa-i nufura: "May Allah increase us in humility even as the enemies are increased in their hatred."
 

And when it is said to them, "Prostrate to the Most Merciful," meaning in Urdu

اِن لوگوں سے جب کہا جاتا ہے کہ اس رحمان کو سجدہ کرو تو کہتے ہیں "رحمان کیا ہوتا ہے؟ کیا بس جسے تو کہہ دے اسی کو ہم سجدہ کرتے پھریں؟" یہ دعوت ان کی نفرت میں الٹا اور اضافہ کر دیتی ہے