Allah says consoling His Messenger for the pain and insult caused by the mockery and disbelief of the idolators,
(Indeed (many) Messengers were mocked before you, but the scoffers were surrounded by what they used to mock.) meaning, the punishment which they thought would never come to pass. This is like the Ayah:
(Verily, Messengers were denied before you, but with patience they bore the denial, and they were hurt; till Our help reached them, and none can alter the Words of Allah. Surely, there has reached you the information (news) about the Messengers (before you)) 6:34. Then Allah menitons His favor for His creatures; He protects them by night and by day, taking care of them and watching over them with His Eye that never sleeps.
(Say: "Who can guard and protect you in the night or in the day from the Most Gracious") means, other than the Most Gracious Himself
(Nay, but they turn away from the remembrance of their Lord.) means, they do not recognize the blessings and favor of Allah towards them; they turn away from His signs and blessings.
(Or have they gods who can guard them from Us) This is a rhetorical question aimed at denouncing and rebuking. The meaning is, do they have any gods who can protect them and take care of them other than Us It is not as they imagine or as they claim. Allah says:
(They have no power to help themselves,) these gods on whom they rely instead of Allah cannot even help themselves.
(nor can they be protected from Us.) Al-`Awfi reported from Ibn `Abbas,"Nor can they be guarded from Us."