The Prostration - 32:30 So turn away from them and wait, and they are waiting.
Prophet Muhammad felt responsible because they did not believe. Our Lord reassured him that his duty was only to convey the revelation and that he was not responsible for those who did not believe:
The Poets/26:3 You may be grieving yourself because they do not believe

The Cave/18:6 If they do not believe this, will you blame yourself after them, and will you grieve?

Originator/35:8 What do you say to the one whose evil deed is adorned to him and he considers it good? Allah leads astray whom He wills and guides whom He wills. So do not grieve yourself for them. Allah knows well what they do.

The Rocky Tract/15:88 Do not be jealous of what We have given to some of them and do not grieve over them (the disbelievers). Lower your wings to those who believe.

The Cattle/6:35 If their turning away is too much for you, know that even if you had the power to make a hole in the earth or a ladder in the sky, it would not profit you if you presented a miracle. Had Allah willed, He would have guided them. So do not be among the ignorant.

The Criterion/25:56 We have not sent you except as a bearer of glad tidings and a warner.

The Bee/16:82 If they turn away, your duty is only to convey (the message) clearly.

The Letter Qaf/50:45 We know well what they talk about. You are not a tyrant over them. Admonish those who fear My warnings with this Qur´an.

The Scatterers/51:52 "Thus, whenever a messenger came to those before them, they used to say: "This is a sorcerer"or "This is a madman"."
The Scatterers/51:53 Did they advise one another (to say this)? Indeed, they are a people who transgress.
The Scatterers/51:54 Turn away from them; you are not to be blamed.
The Scatterers/51:55 Remind them, for reminding benefits those who believe.

The Mountain/52:29 You give advice. By the favor of your Lord towards you, you are neither a seer nor a madman.

The Cow/2:119 We have sent you with the truth, a bearer of glad tidings and a warner. You are not responsible for the people of Hell.

Prophet Hud/11:12 "Perhaps your chest will be constricted and you will abandon some of what has been revealed to you because they say, "Should not a treasure have descended to him, or an angel with him?"You are only a warner; Allah is the Controller of all things."

The Opening Up/94:1 Did We not enlarge your chest and make you calm?