New International Version:
And you also were included in Christ when you heard the message of truth, the gospel of your salvation. When you believed, you were marked in him with a seal, the promised Holy Spirit, who is a deposit guaranteeing our inheritance until the redemption of those who are God’s possession—to the praise of his glory.
King James Bible:
In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise, which is the earnest of our inheritance until the redemption of the purchased possession, unto the praise of his glory.
Our inheritance is guaranteed right up until our liberation from the ills and troubles, the frailty and the mortality of this life, when we get our eternal, holy bodies, but what or who is the guarantee and seal?
The word in the Greek, here translated “deposit” or “earnest” also, according to Vine’s, Strong’s and Thayer’s lexicons, means pledge or downpayment, guaranteeing that the full amount will be paid. Meanwhile, the Greek associates the word “holy” with the “promise,” not with the “Spirit,” which would make “the holy promise” the guarantee, not the Holy Spirit. Certainly, the Holy Spirit is not referred to as “the Spirit of promise” anywhere else, and a promise is also known as a pledge, so it would seem that the downpayment is the holy promise.
Now if our inheritance is guaranteed by “the holy promise,” it has to work by faith, because you can only claim on a promise as long as you believe it. Nobody would ever attempt to claim on a promise they were sure was not genuine.
But if the Holy Spirit is the guarantee then it is no longer by faith, since it becomes the responsibility of the Holy Spirit (an all-powerful, sentient being) to honour the promise and ensure our inheritance, come what may. This would rule that you cannot lose your salvation, even if you lose your faith and choose to turn away from Jesus, because it’s not up to you, it’s the responsibility of the Holy Spirit.
However, we have already seen, for example in Galatians 5:4, any attempt to follow the Mosaic law, or Torah, is to fall from grace, cut ourselves off from Christ and jettison our salvation. Also in Ephesians 4:13 we see we must “grow up into one perfect man,” however, if we separate from that by joining a ‘church denomination’ how will we not lose our salvation? So the inheritance is ours by faith, guaranteed by the holy promise.
The Mouse Companion Version (MCV):
And when you heard the word of truth, the gospel of your salvation, and believed in him, you were sealed in him, in the Spirit, with the holy promise, which is the guarantee of our inheritance until the liberation of his purchased possession, to the praise of his glory. >ᴥ<