Verse 4.7 from the Bhagavad Gita states:

“Yada yada hi dharmasya glanirbhavati bharata
Abhyutthanamadharmasya tadatmanam srjamyaham”

This verse means “Whenever there is a decline in righteousness/truth, O Arjuna, and rise of unrighteousness/lies, then I manifest Myself.”

Lord Krishna is saying that he incarnates on Earth whenever there is a decline in morality and truth/righteousness and a rise in immorality and lies/unrighteousness.

The verse is often interpreted as a message of hope and reassurance to those who are struggling to maintain their faith and truth/righteousness in a world that can seem to favor lies. It reminds us that ultimately, truth triumph over lies, and that even in the darkest of times, we are never alone, as the divine is always present and watching over us.