Arabic Saying: Hit the Iron while it's Hot

I am subscribed to the Jordan TV channel RoyaTV on YouTube.  They put up a lot of stuff so I don't watch it all, but today I happened to click on a clip titled على رأي المثل : اضرب الحديد وهو حامي. The show is called على رأي المثل ('ala ra'i almathal) which is how you say in Arabic "as the saying goes".  They go around and ask people what a saying means.  This is absolutely perfect for those learning Arabic.  You get a bunch of different people talking about what common Arabic sayings mean to them.  Since the channel is Jordanian the responses are in Jordanian and Palestinian dialect, but these sayings mean the same thing everywhere.  The saying in this clip is "hit the iron while it's hot".