18. That is, Allah not only directly watches over whatever each person does, and is fully aware of everything he does, but He has also appointed such guardians as accompany him everywhere and keep a full record of all his deeds. This has been stated here to warn those people who live their lives under the delusion that they have been left absolutely free to do whatever they like and shall not be required to render an account of what they did in this worldly life. The warning is that such people invite their own retribution.
19. This is to warn them further that they should not remain under any delusion that some holy person or saint or angel has the power to rescue them from divine retribution, for there is none who could defend them against Allah, even though they might have been paying homage and making offerings to their so called patrons and protectors in the hope that they would rescue them from punishment from Allah on the Day of Judgment.