Since Al Quran was revealed in an environment in which followers of other faiths were present (e.g. Jews/Christians/other) simply saying "obey God" does not differentiate anything if an audience member already believes in God and is following their own holy book etc.
"Other faith"

Or is it actually 'the same faith' after all??
Mind you when Muhammad said those words who are now being written in a book called Quran, the Quran printed edition version is not yet exist..
I always 'suspected' that the message in the Quran was MAINLY directed towards the Jews and Christians audience in the first place.
Given:
1. Nearly 60-70% of its content told stories regarding 'heroes' of the Jews, David, Solomon, Moses etc..
2. It again clarify that Jesus and John was indeed God's prophet and messenger.
3. Some of the message can be 'clearly understood' within 'hebrew/israelite' cultural context.
For example: Those who violated the Sabbath are turned to apes and despised...
Many people interpret the story as if God did literally turned those Sabbath violator people into Apes.
Within hebrew/israelite context; this is an allegorical stories, Apes/Monkey in hebrew culture symbolize "Greed" just like Donkey symbolize "Firmness".
Those who violates the sabbath are cursed to be "Greedy" people / never satisfied or be happy on what they have and not literally turned to monkeys..
Imagine reciting the stories on Moses, David or Solomon to the Chinese during that period..
They will be left dumb and confounded... Who The Heck is Moses?

? And why should I care about him?

?
For the chinese; perhaps the messenger will told stories on Lao Tze or other popular chinese heroes...
Salam / Peace