What is the "double trust" (The Tragedy of Macbeth, Act I, Scene vii, line 12) that Macbeth would be breaking if he kills Duncan?

Macbeth had several impediments to assassinate Duncan, King of Scotland. The double trust he would be braking is that first he considered the King Duncan as his "kinsman and his subject" so he had to protect him. Second, Macbeth was hosting Duncan in his castle so he had to keep it away from any threat as an implicit compromise instead of being himself the killer. In addition, Macbeth thought that King Duncan was a noble, virtuous and free of corruption person, so his dead would make people feel very sad which filled Macbeth with a lot of guilt even though ambition made him doubt.