Why does Macbeth hesitate to murder the king?

Macbeth is aware that murdering king Duncan would be one of the greatest sins and, he is talking about it in Act I, Scene 7:

He's here in double trust; First, as I am his kinsman and his subject, Strong both against the deed; then, as his host, Who should against his murderer shut the door, Not bear the knife myself.

Macbeth states that going after his unchecked ambition which entails killing Duncan is wrong...

Macbeth is aware that murdering king Duncan would be one of the greatest sins and, he is talking about it in Act I, Scene 7:

He's here in double trust;
First, as I am his kinsman and his subject,
Strong both against the deed; then, as his host,
Who should against his murderer shut the door,
Not bear the knife myself.

Macbeth states that going after his unchecked ambition which entails killing Duncan is wrong for three major reasons. Firstly, Macbeth is Duncan's relative, so it is abnormal and sinful to murder him since they are related. Secondly, Macbeth should be Duncan's most loyal subject, so he should fight for him, not kill him. Thirdly, when Duncan arrives at Macbeth's home, Macbeth will be his host, so he should protect Duncan because he will be Macbeth's guest. Macbeth should guarantee that his guest is safe. Additionally, Macbeth proclaims that the king is benevolent, and he has been recently promoted by the king.

All of the reasons listed above are strong enough, and Macbeth should not go against them. Yet, he states that his ambition is the chief reason why he wants to take the throne and eliminate Duncan.