“By this we know that we remain in him and he in us, because he has given us of his Spirit.”
How do we know we have the Spirit of God? We know because we love God and other people. We are not hostile and argumentative towards others, but seek the bond of peace.
“… being eager to keep the unity of the Spirit in the bond of peace.”
To have the Spirit of God dwelling in us brings us spiritual life and peace: spiritual life that knows God and can relate to Him and also peace with Him because our sins are atoned for and we are forgiven.
The work of the Holy Spirit within us is profound. He works in us to want what God wants and to confirm our wandering will to God’s will. He teaches us the things of God and confirms our desires after all good and holy things. All else is from our sinful self, which we fight against every day. The Spirit of God witnesses to us that we belong to God and are set apart for His purposes.
“But you are a chosen people, a royal priesthood, a holy nation, a people for God’s own possession, to proclaim the virtues of Him who called you out of darkness into His marvelous light.”
1 Peter 2:9
We walk through our lives in the light of His glorious love. Love becomes our defining feature and the imprint of the Spirit on our life. Without this mark we have no assurance that we belong to the family of God.
There is also a power given by the Holy Spirit to all who believe. The power that dwells with us is able to give us the courage and strength to face our sin and turn away from it. It is power that ungodly do not possess and is a certain mark that we belong to God. The Christian does not have to sin, indeed is constrained to not sin, but keep the commands of God. God does not leave us on our own but gives us His Spirit that we might follow Him and live our life for His glory.