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Twelfth Night,
Act 3, Scene 4, line 165.

Note to Twelfth Night, 3.4.165, "God have mercy upon one of our souls!"

Sir Toby is reading Sir Andrew Aguecheek's letter, which seems sensible, since every Christian should pray for God to have mercy on his/her soul, but "God have mercy on your soul" is something commonly said to a dying person, so Sir Andrew doesn't want God to have mercy on his soul.

Angus Wright as Sir Andrew Aguecheek
Sir Andrew Aguecheek