riih.qarojamahoamaan,
If, 'We meditate upon the understanding which guides me to know the God's glory which is there in three worlds - physical, mental and spiritual.', do we need to explain or do we need explanations?
Anyway, if you have gone through 'Mindspace', then you will be surprised to know that I have written that before knowing the meaning of this mantra.
I do not need to go into the grammar, I cannot go into a debate, if I have the understanding.
If understood, it also says the divine is within us, as we cannot separate ourselves from the three worlds!
About incarnations - Krishna, Rama, Jesus, Buddha etc. were not born as God's incarnations/messengers. They were considered or believed to be the incarnates/messengers by the way of their teachings/wisdom/knowledge. Their understanding of the three worlds have transcended them to that level.