16 The Spirit itself beareth witness with our spirit, that we are the children of God: (Romans 8:16 KJV)
William Burkitt’s Commentary
Observe here, 1. That our adoption into God’s family is evidenced by the testimony of the Spirit, bearing witness to and with our spirits; here are two witnesses produced to testify the truth of a believer’s adoption, namely, God’s Spirit and his own; the Spirit testifies by laying down marks of trial in the holy scriptures, by working such graces in us as are peculiar to God’s children, and by helping us to discover this work in our own souls more clearly and evidently; our own spirits testify by reflecting upon our general conversation: the Spirit testifies our adoption by evidencing to us our sanctification: And all this is done, not by sudden impulses, and immediate inspirations, which is the witnessing of the Spirit that enthusiasts pretend to, but the Spirit witnesses in a way of argumentation. Thus, whoever repents, believes, and obeys the gospel, says the scripture, shall be saved.
Observe, 2. That a Christian may in this life, without a diving revelation, attain a well-grounded assurance of his adoption and salvation; for the Spirit of God both bears witness to him and bears witness with him as touching the sincerity of his heart and life.
Observe lastly, That there is no safe and secure way to prove our adoption, but by testimonies brought of our sanctification; the privy seal of our adoption must be thus attested under the broad seal of our sanctification; the goodness of our state and condition must be evidenced by the holiness of our lives and conversation.