I was always taught that we should memorize Bible verses (a good thing) that pertain to salvation and go to them when we doubt our salvation and they will give us assurance of salvation. Is this Biblical?

But what is that witness? It is nothing physical, vocal nor psychical. The Spirit never commits Himself to the flesh. The only witness He gives is a subjective one, known to the individual alone. The Spirit announces Himself to the deep, inner spirit of the man. The flesh profiteth nothing, but the believing heart knows. Holy, holy, holy.

The Bible says “it is that very Spirit bearing witness with our spirit that we are children of God,” (Romans 8:16 NRSV) “by putting his seal on us and giving us his Spirit in our hearts as a first installment.” (2 Corinthians 1:22 NRSV) and “He who has prepared us for this very thing is God, who has given us the Spirit as a guarantee.” (2 Corinthians 5:5 NRSV)

The Spirit is our guarantee that we are truly in Him and are saved. The changes the Spirit makes in us are evidence that He is in us.

We are not truly born again unless by the Spirit. “But now we are discharged from the law, dead to that which held us captive, so that we are slaves not under the old written code but in the new life of the Spirit.” (Romans 7:6 NRSV) “For the law of the Spirit of life in Christ Jesus has set you free from the law of sin and of death.” (Romans 8:2 NRSV) “For all who are led by the Spirit of God are children of God.” (Romans 8:14 NRSV)

While the infilling of the Spirit is received by faith and only by faith, let us beware of that imitation faith which is no more than a mental assent to truth. It has been a source of great disappointment to multitudes of seeking souls. True faith invariably brings a witness.