Hebrews 5:9

And being made perfect
In his obedience, through sufferings; having completed his obedience, gone through his sufferings, and finished his sacrifice, and being perfectly glorified in heaven:

he became the author of eternal salvation unto all them that obey
him;
the salvation Christ is the author of is "eternal"; it was resolved upon from eternity, and contrived in it; it was secured in the everlasting covenant, in which not only a Saviour was provided, but blessings both of grace and glory: and it is to eternity; and stands distinguished from a temporal salvation, and is opposed to eternal damnation; it is the salvation of the soul, which is immortal; and it takes in both grace and glory, which are of a durable nature; and the continuance of it is owing to the abiding and lasting virtue of Christ's person, blood, and righteousness: and Christ is the cause or author of this salvation, by his obedience and sufferings; by obeying the precept, and bearing the penalty of the law; by the price of his blood, and by the power of his arm; by his death and by his life; by his sacrifice on the cross, and by his intercession in heaven; by bestowing grace here, and glory hereafter: this shows that salvation is done, and that Christ is the sole author of it, and that all the glory of it should be given to him; and those to whom he is the author of salvation, are such as hearken to the voice of his Gospel, and obey hin in his ordinances. Christ is not the author of salvation to all men; all men do not obey him; all those whom Christ saves, he brings them to an obedience to himself; for his obedience for them does not exempt them from obedience to him, though their obedience is no cause of their salvation; Christ himself is the alone author of that.