Tafsir of Hud 11:112

{So remain on a right course as you have been commanded} Remain on a right course, a steadfastness like the one you were commanded to follow upon the path of truth, without deviating from it.

{And [so should] those who have turned back with you} This is conjoined to the hidden pronoun in fastaqim (remain on a right course). It is permissible to conjoin to it without an emphatic separate pronoun because the intervening phrase (kama umirta) acts as a substitute. The meaning is: "Remain on a right course yourself, and let those who have turned back from disbelief and believed with you also remain on a right course."

{And do not transgress} Do not exceed the limits of Allah.

{Indeed, He is Seeing of what you do} He is All-Knowing, and He will recompense you for it, so fear Him.

From Ibn Abbas: No verse was revealed to the Messenger of Allah (ﷺ) in the entire Qur’an that was more intense or more difficult for him than this verse. For this reason, he said: "Hud, al-Waqi'ah, and their sisters have turned my hair gray."

It is narrated that his companions said to him: "Grayness has come upon you quickly." He replied: "Hud has turned my hair gray."

From some others: I saw the Messenger of Allah (ﷺ) in a dream and said to him: "It is narrated from you that you said: 'Hud has turned my hair gray.'" He said: "Yes." I asked: "What is it in it that turned your hair gray? Is it the stories of the prophets and the destruction of nations?" He replied: "No, but rather His saying: {So remain on a right course as you have been commanded}."

From Ja'far al-Sadiq (may Allah be pleased with him): Regarding {So remain on a right course as you have been commanded}, he said: "Be in need of Allah through the soundness of your resolve."

{And do not incline toward those who do wrong, lest you be touched by the Fire, and you would not have other than Allah any protectors; then you would not be helped.}