Philippians 1:6 (Amplified Bible)
And I am convinced and sure of this very thing, that He Who began a good work in you will continue until the day of Jesus Christ [right up to the time of His return], developing [that good work] and perfecting and bringing it to full completion in you.
What amazing, foolproof, ironclad assurance God gives us! He can be trusted to complete everything He has started. With God, there are no abandoned projects or half-finished books. He finishes every project He begins, and He leaves no goal unreached. When He sets His heart on us, He never gives up! You can be confident that the Seed of Himself, the Word of Truth, that He has planted in you will, in fact, produce fruit. There WILL be a harvest, for the Lord of the Harvest Himself guarantees it.
Isaiah 55:10-13 (Amplified Bible)
10For as the rain and snow come down from the heavens, and return not there again, but water the earth and make it bring forth and sprout, that it may give seed to the sower and bread to the eater,
11So shall My word be that goes forth out of My mouth: it shall not return to Me void [without producing any effect, useless], but it shall accomplish that which I please and purpose, and it shall prosper in the thing for which I sent it.
12For you shall go out [from the spiritual exile caused by sin and evil into the homeland] with joy and be led forth [by your Leader, the Lord Himself, and His word] with peace; the mountains and the hills shall break forth before you into singing, and all the trees of the field shall clap their hands.
13Instead of the thorn shall come up the cypress tree, and instead of the brier shall come up the myrtle tree; and it shall be to the Lord for a name of renown, for an everlasting sign [of jubilant exaltation] and memorial [to His praise], which shall not be cut off.