Does going to the barber and getting a haircut during prayer time entail sins and bring about feelings of regret?

The preponderant opinion among scholars is the obligation of congregational prayer. Therefore, it is not permissible to be preoccupied from it with cutting hair or similar activities, unless delaying them would result in unbearable harm or hardship. There is no evidence that the sin of abandoning congregational prayer is equivalent to the number of hairs on one's head. It is obligatory to seek forgiveness, repent, and be diligent in performing congregational prayers.