Titus 3:5, Eph 2:7-9, Hab 2:4, Rom 1:17
In the Old Testament, the reason the Israelites were able to acquire the land of Canaan was not because of their righteousness, but because of the oath God made to their ancestors, Abraham, Isaac, and Jacob. (Deut 9:5)
Deut 9:5 Not for thy righteousness, or for the uprightness of thine heart, dost thou go to possess their land: but for the wickedness of these nations the Lord thy God doth drive them out from before thee, and that he may perform the word which the Lord sware unto thy fathers, Abraham, Isaac, and Jacob.
In the Old Testament, it is prophesied that people will become righteous by believing in Christ. (Hab 2:4)
Hab 2:4 Behold, his soul which is lifted up is not upright in him: but the just shall live by his faith.
By the grace of God, we have been saved by believing in Jesus as the Christ. (Romans 1:17, Titus 3:5, Ephesians 2:7-9)
Romans 1:17 For therein is the righteousness of God revealed from faith to faith: as it is written, The just shall live by faith.
Titus 3:5 Not by works of righteousness which we have done, but according to his mercy he saved us, by the washing of regeneration, and renewing of the Holy Ghost;
Ephesians 2:7 That in the ages to come he might shew the exceeding riches of his grace in his kindness toward us through Christ Jesus. 8 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: 9 Not of works, lest any man should boast.