"Now the just shall live (F) by faith: but if any man draw back (A), My soul shall have (P) no pleasure in him. But we are not (P) of them who draw back (P) unto perdition; but of them that believe (are believing - actually pistis, meaning "faith," a noun, but used here as a present tense verb) to the saving of the soul" (Heb. 10:38-39).
Notice that I have highlighted the verbs, which are all present (P), future (F), or Aorist (A - both present and future). From these and other verses, it is clear that salvation is the result of faith in Jesus Christ (Eph. 2:8-9), and that salvation results in an immediate sealing of a child of God by the Holy Spirit (Jn. 6:27; 2 Cor. 1:22; Eph. 1:13; 4:30). In other words, a person's salvation has a beginning (Jn. 3:3-8), and continues forever, as salvation is the status of those possessing eternal life (Jn. 3:16; 10:28; 17:2; Rom. 5:21; 6:23; 1 Jn. 2:25; 5:11, 13). Salvation, the result of imputed righteousness (Rom. 4:11, 22-24; 2 Cor. 5:21;Jam. 2:23), is "a gift that lasts much more than a lifetime!"
We can learn much about a saving faith from just these fifteen verses.
 By faith Abel . . . obtained witness that he was righteous . . . .
 By faith Enoch . . . pleased God.
 By faith Abraham . . . obeyed . . . .
 By faith (Abraham) sojourned in the land of promise . . . .
 By faith Abraham . . . offered up Isaac . . . .
 By faith Isaac blessed Jacob and Esau concerning things to come.
 By faith Jacob . . . blessed both the sons of Joseph; and worshipped . . . .
 By faith Joseph, when he died . . . gave commandment concerning his bones.
 By faith Moses . . . was hid three months of his parents . . . .
 By faith Moses . . . refused to be called the son of Pharaoh's daughter . . . .
 By faith (Moses) forsook Egypt . . . seeing Him who is invisible.
 By faith (Israel) passed through the Red sea . . . .
 By faith the walls of Jericho fell down . . . .
 By faith the harlot Rahab perished not with them that believed not . . . .
Notice with the exceptions of Abel and Enoch, all of these listed as great men and women of faith had their "flaws" listed in the Scriptures for all to see, and that they were sinners like you and me. That is good news, because it tells us that we do not have to be perfect to be saved, but simply need to believe God by faith in His only begotten Son (Jn. 6:29)!
Salvation is based upon a present faith which continues to believe in Jesus!