You are reading a tafsir for the group of verses 21:24 to 21:25
أَمِ اتَّخَذُواْ مِن دُونِهِ ءَالِهَةً قُلْ

(Or have they taken for worship gods besides Him Say:) -- O Muhammad --

هَاتُواْ بُرْهَـنَكُمْ

(Bring your proof.) your evidence for what you are saying.

هَـذَا ذِكْرُ مَن مَّعِىَ

(This is the Reminder for those with me) means, the Qur'an.

وَذِكْرُ مَن قَبْلِى

(and the Reminder for those before me) means, the previous Books, unlike what you claim. Each Book was revealed to each Prophet who was sent with the message that there is no god except Allah, but you idolators do not recognize the truth, so you turn away from it. Allah says:

وَمَآ أَرْسَلْنَا مِن قَبْلِكَ مِن رَّسُولٍ إِلاَّ نُوحِى إِلَيْهِ أَنَّهُ لا إِلَـهَ إِلاَّ أَنَاْ فَاعْبُدُونِ

(And We did not send any Messenger before you but We revealed to him (saying): "There is no god but I. ..") This is like the Ayat:

وَاسْئلْ مَنْ أَرْسَلْنَا مِن قَبْلِكَ مِن رُّسُلِنَآ أَجَعَلْنَا مِن دُونِ الرَّحْمَـنِ ءَالِهَةً يُعْبَدُونَ

(And ask those of Our Messengers whom We sent before you: "Did We ever appoint gods to be worshipped besides the Most Gracious") 43:45

وَلَقَدْ بَعَثْنَا فِى كُلِّ أُمَّةٍ رَّسُولاً أَنِ اعْبُدُواْ اللَّهَ وَاجْتَنِبُواْ الْطَّـغُوتَ

(And verily, We have sent among every Ummah a Messenger (proclaiming): "Worship Allah, and avoid Taghut (all false deities).") 16:36 Every Prophet who was sent by Allah called people to worship Allah Alone, with no partner or associate. The natural inclination of man (Al-Fitrah) also bears witness to that. The idolators have no proof and their dispute is of no use before their Lord; on them is wrath, and for them will be a severe torment.