It would be good for your life if you didn't

It would be bad for his continued employment prospects if you reported him and used that text as evidence at a tribunal

What a dick

What goes through a persons mind and metaphorical heart in order to say that?
My worker just had an emergency surgical procedure, let me make his life hell by threatening to fire him if he doesn't come to work tomorrow. Logic.

Karma will get him. Make sure the company magically falls apart if he has to take a day off sick! ;)

That's not a good idea... It would tell his bosses boss, if he has one, that he is the one who makes everything run smoothly and therefore he would be the one to receive future raises, position advancements, ETC.

It would be better if this employee had a more efficient day without his bosses direction.

Depends on how you do it. If you make it look like he's a micromanaging dick by constantly asking his superior for stuff that you should have access to, that might work.

Send him a photo of the operation afterward. He'd better be smart enough to believe that. If you still lose your job, then take it to a rights tribunal.

I don't think he can do that...

He texted back? I assume you've already thanked him for the evidence he so kindly provided that you'll be using during the trial?

Take a screen shot of that. Make sure the dates and times of all texts are available. Also make sure his phone number is part of what's there. He can't say someone else texted you that then, OP. Keep all of that if he fires you so you can take it to HR. What your boss said and plans on doing sounds highly illegal.

Also make sure you keep all your paperwork from the hospital and let them know the situation. Your attending physician will write you a note saying you shouldn't be at work for "X" amount of time to recover. I was nearly fired earlier this year for a similar situation, but I worked with HR and kept my job.

Does he even realise you had surgery? What a jerk, take him to church

Why would you take him to church out of all places??? why not court...

It's an expression that means giving him whatfor. (And if you don't know what whatfor is, it's telling someone off.)