In the OT, God's kindliness towards the people of Israel (Zech. 12: 10—a ‘spirit of grace’ in LXX), which consists in the forgiveness of sins (Exod. 33: 19). He gives graces (favours) which are undeserved gifts of his love (Isa. 63: 7). This was the basic meaning of the word which is found in the NT when grace is linked to Jesus, who represents in his person God's graciousness towards mankind. Jesus is himself the fullness of grace and truth (John 1: 14–17). In Paul's thought it is by the grace of God that believers like himself were called, and therefore we are deprived of any grounds for boasting (Rom. 3: 27; 1 Cor. 1: 31); Paul must give God the glory for the free gift of salvation which cannot be earned by his own efforts. There now exists a ‘rule of grace’ (Rom. 5: 21) and to live under grace is to live in the obedience of faith, with holiness as its aim (Rom. 6: 15–22).
What is true of grace, bringing people into the redeemed community, is true equally of the callings to offices (‘apostleship’, Rom. 12: 3) and the other gifts or graces (Rom. 12: 6) which are bestowed on the Body as necessary for its life (1 Cor. 12: 6–8), though these gifts are not of equal importance. The Greek charisma, from charis (a grace), emphasizes the free nature of the gifts received; and, by a slight extension, Paul can use the word charis to mean an acknowledgement of the gift, which leads to thanksgiving—hence the English ‘grace’ before meals.
Paul also mentions grace received in suffering (2 Cor. 12: 9; Phil. 1: 19); and the collection for the Church in Jerusalem is a grace (1 Cor. 16: 3), for it is the work of the spirit who prompts the generosity of believers.
It is indeed difficult to differentiate ‘grace’ from the ‘Holy Spirit’ in the NT. Unfortunately in later Christian theology, under the influence of Augustine, grace came to be regarded as a ‘thing’, a kind of impersonal entity or quasi-physical force or power which lights upon those predestined to absorb it.