How do we know that grace alone is enough for salvation?

According to Galatians 6:15, the Apostle Paul asserts that external practices such as circumcision do not contribute to one's standing before God. The essence of salvation lies in being a new creation through faith in Christ. This foundational truth confirms that our relationship with God is established solely on His grace, and that our works or adherence to the law cannot add to the finished work of Jesus Christ. Therefore, believers rest in the sufficiency of Christ alone for their salvation, rejecting any doctrine that seeks to impose additional requirements beyond faith.