Clothes going through Character

Hey, the clothes of my blender model are clipping through my character when I move the armature at all, can someone please tell me how I would fix this???

This is the video of the issue: (I couldnt use the attachments because It broke)

The shirt needs to be weighted the same as the body. You can use the Transfer Weights tool in vertex weight painting mode.
Also, make sure the armature modifiers for both the body and shirt have the same setting for Preserve Volume. Generally you want Preserve Volume on, but either way, the shirt and body have to be set the same.