Those who associated with Allah will say, "If Allah had willed, we (6:148)

﴿سَيَقُولُ الَّذِينَ أَشْرَكُوا لَوْ شَاءَ اللَّهُ مَا أَشْرَكْنَا وَلَا آبَاؤُنَا وَلَا حَرَّمْنَا مِن شَيْءٍ ۚ كَذَٰلِكَ كَذَّبَ الَّذِينَ مِن قَبْلِهِمْ حَتَّىٰ ذَاقُوا بَأْسَنَا ۗ قُلْ هَلْ عِندَكُم مِّنْ عِلْمٍ فَتُخْرِجُوهُ لَنَا ۖ إِن تَتَّبِعُونَ إِلَّا الظَّنَّ وَإِنْ أَنتُمْ إِلَّا تَخْرُصُونَ﴾
[ الأنعام: 148]

6:148 Those who associated with Allah will say, "If Allah had willed, we would not have associated [anything] and neither would our fathers, nor would we have prohibited anything." Likewise did those before deny until they tasted Our punishment. Say, "Do you have any knowledge that you can produce for us? You follow not except assumption, and you are not but falsifying."

The idolaters will say, using Allah’s will and decree as proof for their associating partners with Him: If Allah had willed that neither we nor our ancestors associate any partners with Him we would not have done so; and if He had willed that we do not make anything unlawful for ourselves we would not have done so.
Those before them also denied their messengers with similar worthless proofs saying: If Allah had willed that we do not prohibit them, we would not have done so.
So they persisted in their denial until they tasted My punishment that I sent down on them.
Say, O Messenger, to these idolaters: Do you have any evidence that indicates that Allah is pleased that you associate others with Him, and that you make lawful what He has prohibited, and make unlawful what He has allowed? Just because you did these actions does not mean that He is pleased with them.
You are following nothing but speculation with respect to this and speculation holds no weight against the truth.
You are only lying.

Those who took partners (in worship) with Allah will say: "If Allah had willed, we would not have taken partners (in worship) with Him, nor would our fathers, and we would not have forbidden anything (against His Will)." Likewise belied those who were before them, (they argued falsely with Allah's Messengers), till they tasted of Our Wrath. Say: "Have you any knowledge (proof) that you can produce before us? Verily, you follow nothing but guess and you do nothing but lie."

phonetic Transliteration

Sayaqoolu allatheena ashrakoo law shaa Allahu ma ashrakna wala abaona wala harramna min shayin kathalika kaththaba allatheena min qablihim hatta thaqoo basana qul hal AAindakum min AAilmin fatukhrijoohu lana in tattabiAAoona illa alththanna wain antum illa takhrusoona

Abdullah Yusuf Ali - Translation

Those who give partners (to Allah) will say: "If Allah had wished, we should not have given partners to Him nor would our fathers; nor should we have had any taboos." So did their ancestors argue falsely, until they tasted of Our wrath. Say: "Have ye any (certain) knowledge? If so, produce it before us. Ye follow nothing but conjecture: ye do nothing but lie."

Safi-ur-Rahman al-Mubarakpuri

Those who committed Shirk say: "If Allah had willed, we would not have commited Shirk, nor would our fathers, and we would not have forbidden anything (against His will)." Likewise belied those who were before them, till they tasted Our wrath. Say: "Have you any knowledge (proof) that you can produce before us Verily, you follow the Zann and you do nothing but lie."

Page 148 English transliteration