Salamu Alykum
Dear Brother Wakas
If I may give my opinion on the question you asked Brother Hassan A.
What I think your trying to bring out of Brother Hassan is that the Quran does not make any mention of specific fine information like how many times in prayer one has to bow and the rate of zakat and so on... And that muslims who are Quran centric tend to somehow resort to practices that are not explained in fine detail in the Quran.
I believe this is what your trying to get to? Correct me if I'm wrong.
What is really important is that the Quran furnishes all the important details of what would be required of prayer, hajj, zakat, fasting etc. I do agree and so do all the Quran centric folk that the Quran does not explain fine details. There seems to be a very important reason why.
GOD wants people to use their abilities to THINK, and put into PRACTICE what He has ordered. If GOD willed He could of been more specific, but He did want people to use their minds and to come up with a systematic way of performing what He has ordered. There is a great example of this in the story of Moses when he told his people that GOD commands you to sacrifice a cow (2:67-2:71). I believe the Prophet was humble enough to take wisdom from this story.
He did not want to be like them and ask so many questions and act like he did not know how. He understood that GOD wants and allows people to THINK. He did not cry out to GOD after GOD has specified in the Quran loads of details of all aspects and tell him I'm still confused. Can you explain more to me. Or that there was an absence of form.
No, He took what He believed was fully detailed and worked with what He was given. If their was anything wrong with the ways he performed his duties then it would of been made mention in the Quran.
The Prophet did indeed use his brain to come up with a system of zakat, a system of prayer, a system of upholding justice, and a system of fasting that would add the finer detail of what we see not included in the Quran.
And also there is more great wisdom in why there is a absence of finer detail regarding the aspects you mentioned. For example, believing Muslims who ALWAYS look to the Quran as their source of guidance from generation to generation would realize that their rate of zakat would need to be changed revolving around the situations they are in. The ritual prayers might be performed differently according to the situations they encounter.
Please see this article below
A SIMPLE INSTRUCTION CONFOUNDS MANY - 'ESTABLISH SALAAT'
https://www.facebook.com/joseph.a.islam/posts/487157614754704Salam dear brothers