Do I have to have a SIM card to send messages.

No. An iPad can send iMessages to other Apple devices over Wifi. No sim card necessary.

Yo send SMS text messages to non Apple devices it requires a paired iPhone over Continuity to send. Having a sim card in the iPad does not change this requirement either.

The Sim card in an iPad is only to access cellular data for internet access when not on Wifi. It is not required for anything else.

Hi, my name is Jayson and no you don’t as long as you have logged into your Apple ID and confirmed it on one of your Apple devices then you can send messages of your iPad.