Macbeth: Act 3, Scene 3

            Enter three MURDERERS.

       First Murderer
  1    But who did bid thee join with us?

       Third Murderer

       Second Murderer
2-4. He ... just:  we don't need to distrust him, since he states our duties and what we have to do exactly the same way as the original instructions [from Macbeth].
  2    He needs not our mistrust, since he delivers
  3    Our offices and what we have to do
  4    To the direction just.

       First Murderer
                                      Then stand with us.
  5    The west yet glimmers with some streaks of day;  
6-7. Now ... inn: i.e., now a belated traveler will urge his horse onward at a faster pace in order to reach an inn in time to avoid danger.
  6    Now spurs the lated traveller apace
  7    To gain the timely inn; and near approaches
  8    The subject of our watch.

       Third Murderer
                                                Hark! I hear horses.

       BANQUO [From offstage.]
9. Give us a light there, ho! Banquo is asking whoever can hear him to provide some light. The idea seems to be that at this place, where the custom is to dismount and send the horses by a longer way, it's expected that attendants will be waiting to escort guests to Macbeth's castle. 10. within the note of expectation: on the list of expected guests.
  9    Give us a light there, ho!

       Second Murderer
                                                Then 'tis he; the rest
 10    That are within the note of expectation
 11    Already are i' the court.

       First Murderer
11. go about: go around the long way. (On Shakespeare's stage, horses are often mentioned, but never seen.)
                                              His horses go about.

       Third Murderer
Image Source: WatsonWork11
 12    Almost a mile: but he does usually,
 13    So all men do, from hence to the palace gate
 14    Make it their walk.

       Second Murderer
                                      A light, a light!

            Enter BANQUO, and FLEANCE with a torch.

       Third Murderer
                                                                    'Tis he.

       First Murderer
15. Stand to't: i.e., let's go; time to do the business we're here for.
 15    Stand to't.

 16    It will be rain tonight.

       First Murderer
                                                Let it come down.

            [They set upon Banquo.]

 17    O, treachery! Fly, good Fleance, fly, fly, fly!
18. Thou mayst revenge: This is said to Fleance. Banquo means that if Fleance flees and lives, he may have a chance to revenge his father's death. O, slave! This is probably the insult that Banquo throws at whichever murderer kills him..
 18    Thou mayst revenge. O slave!

            [Dies. Fleance escapes.]

       Third Murderer
19. Who did strike out the light?: Third Murderer is probably unhappy because the lack of light aided Fleance's escape.
 19    Who did strike out the light?

       First Murderer
Wast not the way?: i.e., wasn't that what we were supposed to do?
                                                      Wast not the way?

       Third Murderer
 20    There's but one down; the son is fled.

       Second Murderer
                                                                  We have lost  
 21    Best half of our affair.

       First Murderer
 22    Well, let's away, and say how much is done.

Exeunt: Banquo's body is probably dragged out, which would be hard on the actor playing Banquo, but a fitting end to this brutal scene.