"He who is without sin cast the first stone" could be understood as a call for humility and self-awareness before judging or condemning others.
In essence, it's a reminder that everyone has flaws, makes mistakes, or has aspects of their lives that they may not be proud of. Passing judgment on others without acknowledging one's shortcomings can be hypocritical. The phrase encourages people to approach situations with empathy and understanding, recognizing the shared human experience of facing challenges and making errors.