What is the way to deal with a husband who constantly insults his wife in front of their children and others, despite being a man of prayer and fearing God?

You must be patient and advise your husband kindly, reminding him of God and the Last Day, and supplicating for his guidance. You should also hold yourself accountable and repent to God, for what has befallen you may be due to sins you have committed. There is no harm in seeking assistance from his parents, his elder brothers, or those he respects, to advise and guide him concerning good companionship, acting upon His (Allah's) saying: "And live with them in kindness" and "And due to them is similar to what is due from them in a reasonable manner."