When Adam and Eve ate of the tree of tree of knowledge of good and evil, their desire transformed their knowledge of true and false into good and evil, so it clouded their judgement where they could never be certain whether a particular action was truly morally good or whether it was just something that they desired. So God's word provides the clarity of moral truth that our desire clouds and that truth is based on God's nature or character traits. The Bible often uses the same terms to describe the nature of God as it does to describe the nature of God's law, which is because it is God's instructions for how to act in accordance with His nature, such as with it being holy, righteous, and good (Romans 7:12), or with justice, mercy, and faithfulness being weightier matters of the law (Matthew 23:23). Likewise, God's ways reveal His nature and teach us how to express His character traits, and there are many verses that describe the Torah as being instructions for how to walk in God's ways, such as Deuteronomy 10:12-13, Isaiah 2:2-3, Joshua 22:5, Psalms 103:7, and many others.
So this is why the Torah is truth (Psalms 119:142) and trustworthy (Psalms 19:7, Nehemiah 9:13). Jesus is the exact expression of God's nature (Hebrews 1:3), so he expressed only God's nature through his actions and what that looked like was sinless obedience to the Torah, so he is the personification of the truth (John 14:6). This is also why 2 Timothy 3:8 says that those who oppose Moses also oppose the truth and why partaking in God's nature is established in truth (2 Peter 1:3-12). The Spirit has the role of leading us in truth (John 16:3), the Spirit has the role of leading us to obey the Torah (Ezekiel 36:26-27), and again the Torah is truth.
