This is very strange! I left some remarks under this request earlier and they seem to have disappeared completely, along with the requester's reply
This is 15th century Dutch so not so easy to understand. What I think it says is
When the lord of the world, the devil, is preparing to devour (you), let us Christian lambs (Christian flock) begin the fight (battle).
It took me a bit of research because I have never heard of any word coming close to 'carpeens', but all books and museums I can find on the internet seem to agree it is not 'carpeens' but 'schapen'
One page says this text, which seemingly could be found on a fair few boats, was taken from the Bible and it does seem Biblical language but where it says I should look for it ('letters of Peter and Paul') I can't find it. Let me know if you have found it! I'd love to see this!