Neyat or intension is the actuall thing islam requires from a Muslim. You can understand it like this. There are lot's of verses and ahadees. The ayats and ahadees are to act upon. When sahaba r.a heard the versus of the holy Quran they knew what Allah SW is asking but how to perform the act and with what spirit(Kafiaat), they did not know in the first, but then they saw Prophet SAW acting and telling how to do the deed.
The main thing in this is called Ahsan. It means a muslim when doing any work should always think Allah SWT is looking all of my deeds and thinkings. The important thing is that when doing a deed we need to think Allah SWT is looking at our acts THROUGH OUT our acts not just in the beggining. The purpose is to produce a spirit that every time to think about Allah SW. When this is achieved no one will act sins or if acted he will immediately ask for forgiveness.
When Sahaba r.a made Wazoo they first used to think what Prophet SAW told them about it then they start Wazoo believing Allah SWT looking at out Niyat and we are gainging all benefits (Fazail) what Prophet SAW told. In other words, they gave all of their concentration to Allah SW. this made their connection to Allah SW strong. They did not do things in ignorance(Ghaflat) as people usually do today. So this way connection between Allah SW and a muslim becomes deep and the muslim act always positive things.
The one more simple example is that when we meet some higher grade person we do not see here and there and talk to him in ignorance. So those who understand the Greatness of Allah SW do not put their concentration somewhere else while doing the work for the sake of Allah.
I may not be very clear as i am not native English. If you know Urdu Language you can read this from page 221 to 225 which explains much much better.
I found that i need to add this explanation
Today, we are under misconception regarding understanding what Neyat or intention actually is.
Intention require some important things which we mulims usually completely ignore today.
- Belief to gain Allah's seek
- Do the deeds as worship not as routine work
- Do the deeds with interest which we completely lack
- Do the deeds believing it is my need and I need it badly
- Hope that Allah SWT will accept
- Dread that my deeds can be rejected
- Actually behave after the deed that it was done due to Allah SWT's Fazl and was out of my strength. If it weren't for the sake of Allah Swt I couldn't do it.
- Do not act as 'we do not need it if it is accepted or rejected we just have done our duty and that's all
We should also remember that all the promises are to act with correct intention. If the ignorance takes the place of intention then we can not get anything.
the final thing is that when a rule is defined by Allah SWT or Prophet SAW that is the rule. And all
other methods are in vein. For example, In the Morning prayer the number of Rakat is 2. If somebody
prays 3 it will not be accepted. If some one insist for the proof then defining it 2 is the actually proof. So I think this way your question has been answered.