I would have wanted to keep this one shorter, but this excerpt from Thomas Watson (c. 1620-1686), A Body of Divinity, p. 236-239, is just so good that I simply had to post the whole thing. Watson here offers us signs by which we may discern whether we have truly been adopted by God as his children:
“Try whether you are adopted. All the world is divided into two ranks, the sons of God, and the heirs of hell. To them he gave power to become the sons of God.’ John 1:12. Let us put ourselves on a trial. It is no sign we are adopted sons, because we are sons of godly parents. The Jews boasted that they were of Abraham’s seed, and thought they must needs be good, because they came of such a holy line. But adoption does not come by blood. Many godly parents have wicked sons; Abraham had an Ishmael; Isaac an Esau. The corn that is sown pure brings forth grain with a husk; so from him who is holy the child springs that is unholy. So that, as Jerome says, non nascimur filii [We are not born sons]; we are not God’s sons as we are born of godly parents, but by adoption and grace. Well, then, let us try if we are the adopted sons and daughters of God.
The first sign of adoption is obedience. A son obeys his father. I set before the sons of the house of the Rechabites pots full of wine, and cups, and said unto them, Drink ye wine. But they said, We will drink no wine: for Jonadab the son of Rechab our father commanded us, saying, Ye shall drink no wine.’ Jer 35:5. So, when God says drink not in sin’s enchanted cup, an adopted child says, my heavenly Father has commanded me, and I dare not drink. A gracious soul not only believes God’s promise, but obeys his command. True child-like obedience must be regular, which implies five things:
(1.) It must be done by a right rule. Obedience must have the word for its rule. Lydius lapis [This is the touchstone]. To the law and to the testimony.’ Isa 8:20. If our obedience be not according to the word, it is offering up strange fire; it is will worship; and God will say, Who has required this at your hand? The apostle condemns worshipping of angels, which had a show of humility. Col 2:18. The Jews might say that they were loath to be so bold as to go to God in their own persons; they would be more humble, and prostrate themselves before the angels, desiring them to be their mediators to God. Here was a show of humility in their angel worship; but it was abominable, because they had no word of God to warrant it; it was not obedience, but idolatry. Child-like obedience is that which is consonant to our Father’s revealed will.
(2.) It must be done from a right principle, from the noble principle of faith. The obedience of faith.’ Rom 16:66. Quicquid decorum est ex fide proficiscitur [All acceptable works proceed from faith]. Augustine. A crab-tree may bear fruit fair to the eye, but it is sour because it does not come from a good root. A moral person may give God outward obedience, which to the eyes of others may seem glorious; but his obedience is sour because it comes not from the sweet and pleasant root of faith. A child of God gives him the obedience of faith, and that meliorates and sweetens his services, and makes them come off with a better relish. By faith Abel offered a better sacrifice than Cain.’ Heb 11:1.
(3.) It must be done to a right end. Finis specificat actionem [The end determines the value of the deed]; the end of obedience is glorifying God. That which has spoiled many glorious services, is, that the end has been wrong. When thou doest shine alms, do not sound a trumpet, as the hypocrites do, that they may have glory of men.’ Matt 6:6. Good works should shine, but not blaze. If I give my body to be burnt, and have not charity, it profits me nothing.’ I Cor 13:3. The same I must say of a sincere aim; if I obey never so much, and have not a sincere aim, it profits me nothing. True obedience looks at God in all things. That Christ may be magnified.’ Phil 1:10. Though a child of God shoots short, yet he takes a right aim.
(4.) True child-like obedience must be uniform. A child of God makes conscience of one command as well as another. Quicquid propter Deum fit aequaliter fit [All things done for God are done with equal zeal]. All God’s commands have the same stamp of divine authority upon them; and if I obey one precept because my heavenly Father commands me, by the same rule I must obey all. As the blood runs through all the veins of the body, and the sun in the firmament runs through all the signs of the zodiac; so true child-like obedience runs through the first and second table. When I have respect unto all thy commandments.’ Psalm 119:9. To obey God in some things of religion and not in others, shows an unsound heart; like Esau, who obeyed his father in bringing him venison, but not in a greater matter, as the choice of his wife. Child-like obedience moves towards every command of God, as the needle points that way which the loadstone draws. If God call to duties which are cross to flesh and blood, if we are children, we shall still obey our Father.
But who can obey God in all things?
Though an adopted heir of heaven cannot obey every precept perfectly, yet he does evangelically. He approves of every command. I consent to the law, that it is good.’ Rom 7:16. He delights in every command. O how love I thy law!’ Psalm 119:97. His desire is to obey every command. O that my ways were directed to keep thy statutes!’ Psalm 119:9. Wherein he comes short, he looks up to Christ’s blood to supply his defects. This is evangelical obedience; which, though it be not to satisfaction, it is to acceptation.
(5.) True childlike obedience is constant. Blessed is he that doeth righteousness at all times.’ Psalm 106:6. Child-like obedience is not like a high colour in a fit, which is soon over; but like a right sanguine complexion, which abides; and like the fire on the altar, which was kept always burning. Lev 6:13.
The second sign of adoption is to love to be in our Father’s presence. The child who loves his father is never so well as when he is near him. Are we children? We love the presence of God in his ordinances. In prayer we speak to God, in the preaching of his word he speaks to us; and how does every child of God delight to hear his Father’s voice! My soul thirsteth for thee, to see thy glory so as I have seen thee in the sanctuary.’ Psalm 63:3, 2. Such as disregard ordinances are not God’s children, because they care not to be in God’s presence. Cain went out from the presence of the Lord.’ Gen 4:16. Not that he could go out of God’s sight, but the meaning is, Cain went out from the church and people of God, where the Lord gave visible tokens of his presence.’
The third sign of adoption is to have the guidance of God’s Spirit. As many as are led by the Spirit of God, they are the sons of God.’ Rom 8:14. It is not enough that the child have life, but it must be led every step by the nurse; so the adopted child must not only be born of God, but have the manuduction of the Spirit to lead him in a course of holiness. I taught Ephraim also to go, taking them by their arms.’ Hos 11:1. As Israel was led by the pillar of fire, so God’s children are led by the Spirit. The adopted ones need God’s Spirit to lead them, since they are apt to go wrong. The fleshy part inclines to sin; the understanding and conscience are to guide the will, but the will is imperious and rebels; therefore, God’s children need the Spirit to check corruption and lead them in the right way. As wicked men are led by the evil spirit – the spirit of Satan led Herod to incest, Ahab to murder, Judas to treason – so the good Spirit leads God’s children into virtuous actions.
But enthusiasts pretend to be led by the Spirit, when it is an ignis fatuus, a delusion.
The Spirit’s guidance is agreeable to the Word; enthusiasts leave the Word. Thy Word is truth.’ John 17:17. The Spirit guides into all truth.’ John 16:13. The Word’s teaching and the Spirit’s leading agree together.
The fourth sign is, that if we are adopted we have an entire love to all God’s children. Love the brotherhood.’ I Pet 2:17. We bear affection to God’s children, though they have some infirmities. There are spots in God’s children; Deut 32:2; but we must love the beautiful face of holiness though it has a scar in it. If we are adopted, we love the good we see in God’s children: we admire their graces, we pass by their imprudencies. If we cannot love them because they have some failings, how do we think God can love us? Can we plead exemption? By these signs we know our adoption.”
– Thomas Watson (c. 1620-1686), A Body of Divinity, p. 236-239