Remember therefore from whence thou art fallen, and repent, and do the first works; or else I will come unto thee quickly, and will remove thy candlestick out of his place, except thou repent. Remember - Consider the state of grace in which you once stood; the happiness, love, and joy which you felt when ye received remission of sins; the zeal ye had for God's glory and the salvation of mankind; your willing, obedient spirit, your cheerful self-denial, your fervor in private prayer, your detachment from the world, and your heavenly-mindedness. Remember - consider, all these.
Whence thou art fallen - Fallen from all those blessed dispositions and gracious feelings already mentioned. Or, remember what a loss you have sustained; for so εκπιπτειν is frequently used by the best Greek writers.
Repent - Be deeply humbled before God for having so carelessly guarded the Divine treasure.
Do the first works - Resume your former zeal and diligence; watch, fast, pray, reprove sin, carefully attend all the ordinances of God, walk as in his sight, and rest not till you have recovered all your lost ground, and got back the evidence of your acceptance with your Maker.
I will come unto thee quickly - In the way of judgment.
And will remove thy candlestick - Take away my ordinances, remove your ministers, and send you a famine of the word. As there is here an allusion to the candlestick in the tabernacle and temple, which could not be removed without suspending the whole Levitical service, so the threatening here intimates that, if they did not repent, etc., he would unchurch them; they should no longer have a pastor, no longer have the word and sacraments, and no longer have the presence of the Lord Jesus.