But the second mention is plural "Ouranois", "on earth as it is in the Heavens". I am sure there is some subtle mystical teaching hidden in the singular and plural use of the word Heaven in the Lords Prayer.
In Lords Prayer, a most interesting phrase is "give us this day OUR DAILY BREAD".
IN Greek, "our daily bread" is "arton eemon ton EPI-OUSION", which LITERALLY means "the bread which is ABOVE BEING (ousia,existence)".
Elsewhere, Jesus teaches "Do not worry what you shall eat. The birds do not sow or reap, but are fed". So wouldn't it be strange for Jesus to teach people to pray for "daily bread" in the Lords Prayer?
The interesting interpretation of the Lords Prayer is that one is not asking for "daily bread" in the sense of Wonderbread in the grocery store, but the Eucharist , the "super-substantial" bread.
This goes hand in hand with the verse from the Epistles:
James 1:17 Every good gift and every perfect gift is from above, and cometh down from the Father of lights, with whom is no variableness, neither shadow of turning.
The early Greek Church Fathers asked, "Why does this verse say every GOOD gift, AND every PERFECT gift?" (i.e. why the redundancy)?
They answered that every Good gift is the rain, sunlight, crops, fruitfulness of the earth, but every PERFECT gift is the SACREMENTS, the Eucharist, Baptism, Unction.