Henry Fuseli
The picture is based on a scene from Shakespeare's Macbeth (Act II scene 2) and represents the moment immediately after Macbeth has murdered Duncan, King of Scotland, who had been a guest at his castle.
Macbeth staggers forward, staring in horror, and still grasping the bloody daggers with which he has committed the deed. He tells his wife, “I am afraid to think what I have done; Look on't again I dare not.” It is at this point in the play that Lady Macbeth seizes control. “Infirm of purpose!” she responds to her husband, “Give me the daggers.”
Fuseli was introduced to Shakespeare's plays while studying in Zürich with the Swiss scholar Jacob Bodmer. While in Switzerland, he translated Macbeth into German. In 1766 he attended a production of the play in London, with celebrated actors David Garrick and Mrs. Pritchard in the lead roles. Inspired by this particular scene, he made the drawing I have done the deed (c.1766, Kunsthaus, Zürich), similar in composition to Lady Macbeth Seizing the Daggers (c.1812, Tate, London), but more realistic in approach.
The Tate picture, instead, is known as Mrs. Siddons as Lady Macbeth, and may have been inspired by Mrs Siddons' acting (but it is clearly not a portrait). Mrs. Siddons first played the part of Lady Macbeth at Drury Lane in 1785, and it became one of her most celebrated roles. She even chose it for her farewell performance on June 29th, 1812.