What is the ruling on saying: "Do not forget Allah, lest He forget you"?

Linguistically, nisyan (forgetfulness) is the opposite of dhikr (remembrance) and memorization, and it can also mean abandonment. Nisyan has two meanings: one is to abandon due to heedlessness and inadvertence, and this meaning is negated from Allah the Almighty. The other is to abandon intentionally, and this is affirmed for Allah the Almighty as a punishment for some of His servants. This occurs in retaliation for the servant's forgetfulness of his Lord's command, for "(They forgot Allah, so He forgot them)," meaning Allah abandoned them from His mercy and guidance. This is a matter of requital and retribution.