'Take Heed' in the Bible

so that the Lord may fulfill His promise concerning me, saying, ‘If your sons are careful regarding their way [of life], to walk before Me in truth with all their heart and mind and with all their soul, you shall not fail to have a man (descendant) on the throne of Israel.’

Now therefore, O Lord, the God of Israel, keep for Your servant my father David that which You promised him when You said, ‘You shall not be without a man (descendant) to sit on the throne of Israel, if only your sons take heed to their way [of life] to walk before Me [according to my laws] as you have done.’