Acts 2:21 - Ellicott's Commentary On The Whole Bible

Whosoever shall call on the name of the Lord... — Singularly enough, the precise phrase, to “call upon” God, common as it is in the Old Testament, does not occur in the Gospels. With St. Luke and St. Paul it is, as it were, a favourite word (Acts 7:59; Acts 9:14; Romans 10:12; 1 Corinthians 1:2). Its Greek associations gave to the “invoking” which it expressed almost the force of an appeal from a lower to a higher tribunal. (Comp. Acts 25:11; Acts 25:21; Acts 25:25.) Here the thought is that that Name of the Eternal, invoked by the prayer of faith, was the one sufficient condition of deliverance in the midst of all the terrors of the coming day of the Lord.