Examine what the porter says about alcohol. This is very funny but how is it purposeful in its relations to the larger action of the play?

In a scene of comic relief, the Porter hears knocking at the gate and imagines that he is the porter at the door to Hell. He imagines admitting a farmer who has committed suicide after a bad harvest, an "equivocator" who has committed a sin by swearing to half-truths, and an English tailor who stole cloth to make fashionable clothes and visited brothels. Since it is "too cold for hell" at the gate, he opens the door instead of continuing with a longer catalogue of sinners (16). Outside stand Macduff and Lennox, who scold him for taking so long to respond to their knowcking. The Porter claims that he was tired after drinking until late and delivers a short sermon on the ills of drink.

When the Porter opens the gate for the thanes, he mentions that he and his friends were out "carousing till the second cock" (II iii 23). This statement calls to mind the cock that crows in the New Testament after Peter betrays Jesus by denying knowledge of him (Matthews 26; Luke 22). In Macbeth, the betrayal occurs in a more active form as Macbeth murders Duncan after the crows of the cock.