King David had a yearning and longing and his soul was constantly connected in his devotion to God. It is told that when the Angel of Death came to take his soul, he could not get near him because of his constant adherence to the holy Torah  

Once he went to the bathhouse, a place where all are naked and you can not engage in Torah and mitzvoth and his spirits fell due to the idleness forced upon him. When he remembered the covenant in his flesh, his mind became settled

This act highlights the uniqueness of the circumcision, whose existence and sanctity are equal at all times. On this level, the Brit Mila is better than any other commandment or spiritual level, as all commandments have a specific time and all spiritual levels may go away during inevitable spiritual downfalls 

Only the commandment of circumcision is performed constantly by male Jews throughout their entire life. This is the meaning of the verse "Walk before me and be whole" – A Wholeness in which all times are equal and through which each and every one is always a Jew and so is always worthy of holiness

 If we really are so securely anchored in our connection with God, it is of no surprise how any Jew – even the biggest sinner – can repent at any given time. The secret is simple and know to all: Once a Jew, always a Jew