How do we know we have the Spirit of God?

In Galatians, Paul asks the Galatian church whether they received the Spirit by the works of the law or by hearing of faith, emphasizing that it is through faith that the Holy Spirit is given. The presence of the Holy Spirit in a believer's life is evidenced by a transformed heart, the ability to cry out 'Abba, Father,' and the spiritual fruit produced as a result of His indwelling. This spiritual work brings assurance and affirms our identity as children of God. Romans 8:16 states that the Spirit bears witness with our spirit that we are children of God, therefore confirming our relationship with Him.