Which two factors influence macbeths decision to kill king duncan

Firstly, the three 'weird sisters' (the witches) tell Macbeth that he will become king - 'all hail Macbeth, that shalt be King hereafter'. They put this idea in his head, which sparks his 'vaulting ambition'. Then his 'dear wife' (Lady Macbeth) hears about their 'supernatural soliciting' and tells him that in order to be king, he must kill Duncan.

Macbeth is initially hesitant about murdering Duncan who he deems to be a great king. But then Duncan names his son, Malcolm, heir to the throne and reignites Macbeth's 'deep and dark desires' to become the reigning Monarch.

Still slightly uncertain, Lady Macbeth threatens his manhood, 'When you durst do it, then you were a man' and Macbeth creeps towards Duncan's chambers, intending to commit the 'horrid deed'. He is further encouraged when a supernatural motif, a 'dagger of the mind' appears before him. On it are 'gouts of blood' and this inspires Macbeth to open the door and instigate Duncan's 'surcease'.