Why is there no prohibition, rebuke, or warning to the Jews and Christians in the verse from Surat Al-Ma'idah (5:18), while there is such in the verses of Surat Maryam (19:88-92), even though both surahs declare God to be free from partners and offspring?

The discourse of Allah to the People of the Book in the Quran varies between encouragement and warning, calling them to repentance and seeking forgiveness, and cautioning them against punishment if they persist in their disbelief.

The discourse in Surat Al-Ma'idah (verse 18) comes as a response to their saying: (We are the children of Allah and His beloved ones). This statement of theirs could mean that they intended for Allah, in His benevolence and mercy, to be like a merciful father, or that they are the children of Allah's messengers. Allah responded to them by saying: (Say, 'Then why does He punish you for your sins?' Rather, you are human beings from among those He created. He forgives whom He wills and punishes whom He wills). This clarifies that they are human beings like others, recompensed for their deeds. Allah forgives whom He wills and punishes whom He wills. This is a warning to them lest they become deluded by the status of their predecessors; rather, they must obey Allah and desist from what He has forbidden them.