What verses of the Quran are there that codemns or gives advice/understanding against this wrong practice?
So you are a Sunni/Salafi huh?
(kidding, its a very good thing, and Sunnis are known to always ask for evidence and not just accept any statement that is said.)
Theres so many, in both Qur'aan and Sunnah, but here are some...
"And they have said (to each other), abandon not your gods : abandon neither Wadd for Suwa, neither Yaguth not Yauq".
Bukhari quoted Ibn Abbas as saying that "The above names were those of pious men among the people of Noah. When these pious men died, Satan suggested to the people of Noah that they erect statues of those pious men in their homes and call the statues by these pious men's names. Thus, people did so, but did not worship the statues. The statues, however, in later generations become idols to be worshipped."
Ibn-ul-Qaiyim said "Noah's people were led to idolatry because they aggrandized their dead by sculpturing their images. Such is the case with most idolaters." (15) Some were made to worship stars, as they believed that stars are influential elements in the universe. Later, they built shrines, appointed gate keepers and custodians and fixed offerings and rites for the stars. The same method still continues, apparently originating from the Sabians, the people of Abraham. Abraham (peace be upon him) argued with his people pointing out to them the falsehood of idolatry. He silenced them with arguments and shattered their idols. Consequently, his people demanded that he be set on fire.
"We noticed that some people made statues of the moon, thinking that the moon controlled the world and, thus, deserved worship. The Magians, adherents of Mazdaism, worship fire; they make many shrines for it and appoint caretakers who do not allow the flame to die out for a single moment. Some groups worship water, believing that it is the origin and source of everything. Other groups worship animals, like horses or cows. Others have worshipped men, alive or dead, while still others have worshipped jinn, trees or angel.(
The Qur'aan says about idol-worshipers..
"Say : who is it that sustains you (in life) from the sky and from earth? Or who is it that has power over hearing and sight? And what is it that brings the living from the dead and the dead from the living? And who is it that rules and regulates all affairs?
They will soon say, Allah. Say : Will you not then show piety to Him'' Yunus 10 : 31.
So they did know Allah, but they just took idols as intercessors.
"If indeed, you ask them who is it that created the heavens and the earth, they would be sure to say, 'Allah'. Say : See you then the things that you invoke besides Allah? Can they, if Allah wills some penalty for me, remove His penalty ? Or if He will some grace for me, can they keep back His grace ?" Zumar 39 : 38.
"They worship, besides Allah, things that neither hurt them nor profit them. And they say : these are our intercessors with Allah." Yunus 10:18.
About the people of prophet Hud, the Quran says, "They said, You came to us, that we may worship Allah alone and give up the cult of our fathers?" The people of prophet Saleh said, "Do you forbid us the worship of what our fathers worshipped?"
"And I follow the ways of my fathers, Abraham, Isaac, and Jacob : Never could we attribute any partners whatsoever to Allah; that comes of the grace of Allah to us and to mankind, yet most men are ungrateful." Yousuf (Joseph) j9 38
The people of Abraham, after they were silenced by argument, said, as stated in the Holy Quran "...We worship idols and we remain constantly in attendance on them. (Abraham) said, ‘Do they listen to you when you call on them or they do you good or harm?’ They said, Nay, but we found our fathers doing." 26 : 70-74.
"Say: O people of the Book! Come to a word that is just and fair between us and you, that we shall worship none but God and that we shall associate no partner along with Him, and that we shall not take others as lords besides God. Then if they turn away, say: Bear witness that we are Muslims." Soorah Aal 'lmraan 3:64.
"And the God to be worshipped is only one God. None has the right to be worshipped except Him, the Most Merciful, the Bestower of Mercy."
"Do not take two objects of worship. Indeed, Almighty God is the only Deity to be worshipped, so fear Him."
"Whosoever calls upon (i.e. supplicates or prays to) other than God, for which he has no proof, then his reckoning is only with his Lord. Indeed the disbelievers will not be successful."
"And ask those of our Messengers whom we sent before you: 'Did We ever appoint objects of worship besides the Most Merciful?"
We have not sent before you from the Messengers, except We inspired to him that He is the only One worthy of worship, so worship Him. [21:25]
Say: Verily I call to my Lord and I do not ascribe any partners to Him at all. [72:20]