This is Christian English - it is English, but not as we know it.
God gives by promises means that the only thing you get from god is his word that he will do whatever he says he will do, and you get that whether you want that or not.
"that we may receive by faith" is very interesting. The normal construction would be "so that we must receive [something] by faith." The use of the modal verb "may" gives the impression of "being allowed to" e.g.
"May I have a piece of cake?"
"Yes, you may."
However, as God is all powerful, and it really does not matter whether we want his promise of not, "may" is entirely inappropriate. Nobody/nothing gives us that permission/allows us to receive whatever it is - it just happens (or does not).
Yet this is how the Christian sees God communications - God's going to do it anyway and somehow we are permitted/allowed to receive whatever it is - there is no real permission but, psychologically, it does put you in a very inferior position.
The only possible meaning of "that we may receive by faith" must be "so that we must blindly trust that the substance of the promises will occur."
It is the denial of personal observation and the acceptance of ignorance.
“Wandering in a vast forest at night, I have only a faint light to guide me. A stranger appears and says to me: 'My friend, you should blow out your candle in order to find your way more clearly.' This stranger is a theologian.”
-- Diderot, c1762