"God bless you" or "God blesses you"?
Is it grammatical or theological?
Grammatical :
God blesses you itu simple present
God bless you itu subjunctive mood.
Theological :
God = satu tapi banyak.
The original term, "May God bless you" was contracted into "God bless you," or sometimes just "God bless."
The verb "bless" is used in this phrase instead of "blesses" because it is in the subjunctive mood. The subjunctive mood expresses a hope, wish, possibility, or opinion. The subjunctive mood is hard to distinguish in modern English because it often has the same form as the indicative mood, which indicates a factual statement. The subjunctive mood is easiest to see in the 3rd person (he, she, it) or in this case "God."
The verb 'bless' in "God blesses you" is the 'present simple' tense form. The present simple is used, among other things, to denote a timeless action or state, something which is always, or habitually or generally true. e.g. "Don't be frightened by Rover. He loves children."
The matter may be literally true, or it may be an assertion that something is so.
So, by saying 'God blesses you', the speaker is making a statement about a (real or perceived) condition of the one being spoken to, saying that they are beneficiaries of God's blessing(s).
http://wiki.answers.com/Q/Why_do_you_say_'God_bless_you'_and_not_'God_blesses_you'
Simple explanation:
God bless you = May God bless you --> it is a wish that God will bless you.
God blesses you --> a statement saying that you are always blessed by God.