There are 7 truths of eternal security that I have adapted and gleaned from the doctrine of soteriology:
Christ's personal statements of assurance (John 10:27-29; 6:39-40). Peter and Paul also add their statements (Philippians 1:6; Hebrews 13:5; Romans 8:35-36; 1 Peter 1:23-25).
Christ's perfect offering (Hebrews 10:14) has made believers perfect, once for all.
Christ's providential covenant (Hebrews 8:7-10:25) of His shed blood declares sovereignty and divinely that believers have eternal life.
Christ's perpetual intercession as our Shepherd (John 10:27; Psalm 23; Hebrews 13:20-21), as our Priest (Hebrews 7:25), as our Judge (Romans 8:33-34), and as our Advocate (1 John 2:1-2; 2 Corinthians 5:19) further secure our salvation.
Christ's provisions through prayer (John 17:17, 24), with His promise of the Holy Spirit (John 14:16-21), and the Holy Spirit's witness (Romans 8:1-2, 16) provide assurance when there is doubt.
Christ's permanent union with believers reveals the fact that believers are new creations (2 Corinthians 5:17), believers experience only one spiritual birth (John 3), believers are joint-heirs with Christ (Romans 8:17; Philippians 3:10), and that believers are God's children.
Finally, there is the blessed promise of God's election. Salvation is based on God's choice of us, not our choice of Him (Matthew 11:27; Luke 10:22; John 6:44; 15:16, 19; Romans 9:15-16). God chose us for salvation before all eternity (Ephesians 1:4; 2 Timothy 1:9). God's choice for us for salvation in eternity past results in our believing in Christ (John 6:37; John 17:2; Acts 13:48; 2 Thessalonians 2:13; 1 Peter 1:2).