In the end of scene 5, how does MB respond to LMB’s ideas about putting on a face of welcome?

Macbeth will make a lousy murderer. He is completely 'freaked out" at the thought of murdering the king. L. Macbeth tells him that he must,

Only look up clear. To alter favor ever is to fear. Leave all the rest to me. Macbeth really says nothing to this other than looking scared.