Acts 2:21

And it shall be, that whosoever shall call upon the name of the Lord shall be saved.

This verse was the text of Peter's address, making it clear that his sermon was primarily concerned with human salvation and the means of its procurement by men. As Boles expressed it:

In the midst of these alarming events and wonders and terrible phenomena that foretold awful judgments, opportunity would be given to all who would "call upon the name of the Lord" to be saved.[30]

The impending judgment against Israel would bring the total destruction of the Holy City; but all of the Jews who became Christians were spared in that disaster; and as it was a type of the final judgment and overthrow of the world itself, Peter's message applied not merely to Israel who first heard it but to all men, as stated in Acts 2:39.

Call upon ... The word thus translated denotes far more than merely pronouncing the Lord's name (Matthew 7:21,22; Luke 6:46).

It is used of being declared to be a dedicated person, as to the Lord, Acts 15:17...to invoke, to call upon for oneself (that is, on one's behalf)...and to call upon by way of adoration, making use of the Name of the Lord, Acts 2:21.[31]

[30] H. Leo Boles, op. cit., p. 40.

[31] W. E. Vine, Dictionary of New Testament Words (Old Tappan, New Jersey: Fleming H. Revell Company, 1940), p. 163.