Heb 10:10-14 is a common “proof-text” by Calvinists to support their soteriology; for an exegesis of this pericope and how it does not, when read exegetically, support Calvinism, see, for example:
Refuting Jeff Durbin on Mormonism and the Atonement (cf. Full Refutation of the Protestant Interpretation of John 19:30 and An Examination and Critique of the Theological Presuppositions Underlying Reformed Theology)
I. Howard Marshall wrote the following about Heb 10:14, which is succinct and insightful:
It is the perfection which Christ gives to believers. By His one sacrifices He has perfected for all time those who are being sanctified (Hebrews 10:14). He bestows upon men His own status as an obedient Son of God and with Him they receive glory from the God whose purpose it is to bring many sons to glory. (I. Howard Marshall, Kept by the Power of God: A Study of Perseverance and Falling Away [Minneapolis, Minn.: Bethany Fellowship, Inc., 1969], 156)
In the endnote for this passage, Marshall also noted:
This means that the sacrifice of Christ is eternal in its validity, not that the perfecting of believers is a once-for-all act incapable of being undone. Perfection here is analogous to justification in Paul. It is not a change of nature which cannot (in theory at least) be reversed. (Ibid., 250 n. 62)