Referring to a result that comes later
The proper way here is to rearrange your paper so that this does not happen. It might be possible to put the theorem into the paper twice. Once in the introduction, possibly without some technical details but with more context and intuition around it and once after the required lemmata a proven with all the technical details. 

The main reason is that the proofs of your various lemmata and theorems depend on one another but you want the dependence to form a tree and not have any loops. If you have a theorem that depends on a lemma proved later on, it could look like the proof of the lemma also depends on the theorem stated earlier on.