Hedraios means seated, fixed, or steadfast — from hedra (a seat or base). It describes something that is firmly seated, immovable, like a building on a solid foundation. In the New Testament it appears in 1 Corinthians 7:37; 15:58 and Colossians 1:23, always in contexts of spiritual stability.
1 Corinthians 15:58 gives hedraios its fullest theological force: 'Therefore, my dear brothers and sisters, stand firm. Let nothing move you. Always give yourselves fully to the work of the Lord, because you know that your labor in the Lord is not in vain.' The resurrection of Christ is the foundation for this immovability — because Christ rose, our work is not futile, and we can be hedraios. Colossians 1:23 urges believers to remain 'established and firm, not moved from the hope held out in the gospel.' Spiritual steadfastness is not stoic willpower but rootedness in resurrection hope.