If you neglect the Old Testament in favour of the New Testament, you are in real danger of neglecting the New Testament in favour of the ‘inner witness of the Spirit’.
The inner witness of the Spirit is a phrase which comes from various places in the Bible, but particularly Romans 8:16 where Paul writes that, ‘the Spirit himself testifies with our spirit that we are God’s children’. The intention seems to be to give specific assurance to believers, ‘that we are God’s children’ but its meaning has has morphed the meaning from the intention of Paul into using ‘however I feel inside’ about something being the measure of it.
This turns the primary measure of God’s word away from his special revelation towards our own internal feelings and assessments. It is true that we are made in the image of God (Genesis 1:27) and that Paul says in 1 Corinthians 2:16, ‘we have the mind of Christ’, yet the Bible is clear about what our ‘inner man’ is like: Proverbs 28:26 tells us that ‘whoever trusts in his own mind is a fool, but he who walks in wisdom will be delivered’. Jesus says that it is from the heart that all our sinful acts spring, for example in Matthew 15:19, He says: ‘out of the heart come evil thoughts—murder, adultery, sexual immorality, theft, false testimony, slander’. Jeremiah 17:9 says, ‘The heart is deceitful above all things and beyond cure. Who can understand it?’ WHY would we willingly follow something which is described that way? The modern mantra of feelings and internal understanding driving everything which is epitomised in the phrase, ‘follow your heart’, couldn’t be more unbiblical if it tried.
Whatever you do don’t follow your heart, LEAD it!
Proverbs 4:23 ‘keep your heart with all vigilance, for from it flow the springs of life’.