Practise is correct for its use as a verb in English. Americans use practice as a verb or noun. The saying was not coined by an American, so.. either way is fine.

So, that's embarrassing. You seem to spend a lot of time worrying about spelling on people's comments and trying to correct them. You even made a post on it. The trouble is when you do that you leave yourself open to ridicule when you then make a correction like the one on here. Australian, British and American English have different spellings for the same words and there are people on here from all over the world. Perhaps just focus on adding something meaningful to the conversation rather than trying to be everyone's inadequate English tutor.

Bazinga!