The Spirit itself beareth witness with our spirit, that we are the children of God. Romans 8:16. HP 144.1
You may have the witness of the Spirit that your ways please God. This is obtained by believing in the Word of God, by appropriating that Word to your own soul. This is eating the bread of life, and this will bring eternal life. Compare scripture with scripture. Study the representation of the life of a true Christian as delineated in the Word of God. HP 144.2
The law of God is the great standard of righteousness. This the apostle declares is holy, just, and good. David says, “The law of the Lord is perfect, converting the soul” (Psalm 19:7). Christ says, “If ye love me, keep my commandments.” ... “He that hath my commandments, and keepeth them, he it is that loveth me: and he that loveth me shall be loved of my Father, and I will love him, and will manifest myself to him” (John 14:15, 21). This is most assuredly the witness of the Spirit.... “If ye keep my commandments”—from the heart—“ye shall abide in my love; even as I have kept my Father's commandments, and abide in his love” (John 15:10). HP 144.3
Those who are obedient to the will of God will not have a hard and miserable time in this life. Hear again the words of Christ: “These things have I spoken unto you, that my joy might remain in you, and that your joy might be full” (verse 11). This is the witness which it is the privilege of all to have—the joy of Christ in the soul through appropriating the word of God ... and bringing the requirements of Christ into the practical life. There is full assurance of hope in believing every word of Christ, believing in Him, being united to Him by living faith. When this is his experience, the human being is no longer under the law, for the law no longer condemns his course of action.... HP 144.4
To them that believe, Christ is precious. His Spirit moving upon the mind and heart of the believer is in perfect agreement with that which is written in the Word. The Spirit and the Word agree perfectly. Thus the Spirit beareth witness with our spirit that we are born of God.28Letter 11, 1897. HP 144.5