The Quran makes it clear that the Word of God is complete in the Quran.
As it says in surah 6 verse 115:
وَتَمَّتْ كَلِمَتُ رَبِّكَ صِدْقًا وَعَدْلًا لَّا مُبَدِّلَ لِكَلِمَاتِهِ وَهُوَ السَّمِيعُ الْعَلِيمُ
Watammat kalimatu rabbika sidqan waAAadlan la mubaddila likalimatihi wahuwa alssameeAAu alAAaleemu
And (has been) fulfilled (the) word (of) your Lord (in) truth and justice. No one can change His words, and He (is) the All-Hearer, the All-Knower.
The claim of the pro-hadith writers that God inspired to Muhammad a revelation other than the Quran, or what they call 'hadith qudsi' (Holy hadith) is in clear violation of surah 6 verse 115.
It is also in violation of surah 17 verse 73 and other verses, for example, surah 69 verse 43-47 where God warns the Prophet not to attribute to God anything other than the Quran: surah 17 verse 73 highlighted below:
Surah 17 Verse 73
وَإِن كَادُوا لَيَفْتِنُونَكَ عَنِ الَّذِي أَوْحَيْنَا إِلَيْكَ لِتَفْتَرِيَ عَلَيْنَا غَيْرَهُ وَإِذًا لَّاتَّخَذُوكَ خَلِيلًا
Wa-in kadoo layaftinoonaka AAani allathee awhayna ilayka litaftariya AAalayna ghayrahu wa-ithan laittakhathooka khaleelan
And indeed, they were about (to) tempt you away from that which We revealed, to you that you invent about Us other (than) it. And then surely they would take you (as) a friend.
So, if we analyse surah 17 verse 73, the verse makes it clear that the discussion which is happening is central to being tempted away from the Quran, and inventions attributed to GOD rather than focusing on the actual revelations revealed by GOD almighty.
And then verses 74 and 74 from surah 17 further elaborate and mention the following:
Surah 17 Verse 7
وَلَوْلَا أَن ثَبَّتْنَاكَ لَقَدْ كِدتَّ تَرْكَنُ إِلَيْهِمْ شَيْئًا قَلِيلًا
Walawla an thabbatnaka laqad kidta tarkanu ilayhim shay-an qaleelan
And if not [that] We (had) strengthened you, certainly, you almost (would) have inclined to them (in) something a little.
Surah 17 Verse 75
إِذًا لَّأَذَقْنَاكَ ضِعْفَ الْحَيَاةِ وَضِعْفَ الْمَمَاتِ ثُمَّ لَا تَجِدُ لَكَ عَلَيْنَا نَصِيرًا
Ithan laathaqnaka diAAfa alhayati wadiAAfa almamati thumma la tajidu laka AAalayna naseeran
Then We (would) have made you double (in) the life, and double (after) the death. Then not you (would) have found for you against Us any helper.
If we go further deeper and examine Surah 69 verses 43-47, to summarise, the verse speaks about:
a revelation (Quran) from the Lord of the worlds. Had he falsely attributed any sayings to Us, We would have grabbed him by the right, and We would have severed his aorta. None of you would be able to prevent it. 69:43-47
I would like to summarise and say that throughout the Quran, there are numerous verses where we are told that the only revelation received by the Prophet Muhammad from God was the Quran.
See the following surahs and verses: 4:105, 5:48, 6:19, 6:92, 6:155, 29:47, 16:89, 39:2, 76:23.
Please verify everything you have read today with the Quran yourself, as it is the only source for guidance.
Peace and Respect!