- Though I do not know what verse says it (if any)
From what I understand is that they are there not for sex.
God has given humans the urge (and pleasure) of sex in this life so that humans keep reproducing and so that the human race does not die out.
In heaven, no new humans are to be born (all humans will have been born, lived, died and been judged). This means, sex will no longer needed (and so, the urge for sex will no longer exist).
They will propably be received as servants that care and look after the man.
Women will receive something similar, but this has not been mentioned in the koran (as humans would propably not understand i.e. they wont be male - men are not the best of carers, and they need to be better carers than women)
Sorry for the messy explanation.