Ques. When is a believer sealed with the Holy Spirit?
"In whom also, after that ye believed (or, "having 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."
Scripture distinguishes between quickening and sealing. The Holy Spirit quickened us when we were dead in sins (Eph. 2:55Even when we were dead in sins, hath quickened us together with Christ, (by grace ye are saved;) (Ephesians 2:5)). He sealed us when, through grace, we believed on the Son of God. The Spirit is the seal which God puts upon those who believe in His Son, as dead, risen, and glorified. The interval between the quickening and the sealing may be moments, months, or years; but there is an interval. We believe that a quickened soul will be a sealed one, for God does not leave His work undone.
How often do you see people in a low, legal, doubting state, going about to establish their own righteousness, full of fears and questionings. They are in Romans 7. They do not know accomplished redemption. They are not delivered. They are quickened, but not sealed. Persons in this state know nothing about the one body. They are virtually in the condition of Old Testament saints. There are many in Christendom in this condition.
Ques. Is it wrong to cherish a foolish thought?
Ans. To "cherish a foolish thought" is most assuredly grieving to that Holy Spirit whereby we are sealed. But if we judge the foolish thought it does not disturb our communion. There is a vast difference between treating evil thoughts as intruders, and providing them with furnished lodgings.