Newton's Third(3rd) Law-- How do you know?

It is no brainer that time and time again we've had example after example of newton's third law that we preferably see this example of it taking place when using weights. Just to refresh what it really illustrating here in terms of physics-- there are two forces present in the picture above that act in pairs which is the force of the bar on the weightlifter and the force of the weightlifter on the bar if you can write it like that then they are 3rd law pairs which is how you know that this is the case.