"For every nation We have appointed a rite" meaning: a pilgrimage and a sacrifice, "which they observe, so do not let them dispute with you regarding the matter" meaning: do not let the polytheists turn you away from that which you are upon; He is saying this to the Prophet, peace be upon him.
Surat al-Hajj from (Verse 69 to Verse 72).
﴿لكل أمة جعلنَا منسكا﴾ أَيْ: حَجًّا وَذَبْحًا ﴿هُمْ نَاسِكُوهُ فَلَا ينازعنك فِي الْأَمر﴾ أَيْ: لَا يُحَوِّلَنَّكَ الْمُشْرِكُونَ عَنْ هَذَا الَّذِي أَنْتَ عَلَيْهِ يَقُولُهُ للنَّبِي عليه السلام.
سُورَة الْحَج من (آيَة ٦٩ آيَة ٧٢).