Let's consider the second part of this verse of scripture from I Thessalonians 5:21, "Test all things; hold fast what is good." To hold fast is to guard from loss, hold down, possess, adhere to firmly and retain faithfully. In this verse it implies, adhere to firmly and retain faithfully, Gods Word. Do not accept anything that sounds good but is not inspired by the Holy Spirit, but hold fast to what is good. Applying these definitions to the words "Hold Fast" it should be apparent that a possiblity exists that the Word of God or the things of God can be taken or stolen from a believer. This is also seen in other verses of scripture.
"Let us hold fast the confession of our hope without wavering, for He who promised is faithful."
(Hebrews 10:23) Let us guard, adhere to firmly and acknowledge the truth of the Gospel of Jesus Christ. Never doubting, being unsteady, wavering in the promises or declarations made to believers in Gods Word through Christ, because God is faithful, He does not nor cannot lie. Again, believers are to hold fast, guard from loss, adhere to firmly and retain faithfully Gods Word. In Revelations 2:25 Jesus speaking to the church at Thyatira says, "But hold fast what you have till I come."
Jesus is pointing out another level of what holding fast indicates. For believers to hold fast to Gods Word implies a struggle that someone or something is trying to wrestle it away from them. In this church Jesus reveals as Jezebel was a self-proclaimed prophetess to king Ahab her husband and the influence that she had over him which influenced Gods people in a negative way, that there were false prophetesses in this church that were influencing many with false carnal doctrine. However, Jesus encourages the ones that had not accepted this false doctrine to guard from loss, adhere to firmly and retain faithfully His Word no matter what it takes until He returns which will mark the end of their conflict with evil. This then brings us back to why it is so important for believers to fully understand the Parable of the Soils. It reveals how much we must gurad ourselves from the wiles of the devil.
And these are the ones by the wayside where the word is sown. When they hear, Satan comes immediately and takes away the word that was sown in their hearts. (Mark 4:15) Again, it is very apparent that the Word of God can be taken, robbed, stolen from believers if they do not have a foundation of Gods Word to build upon and hold fast to. Believers are in a conflict, a struggle… "Beloved, while I was very diligent to write to you concerning our common salvation, I found it necessary to write to you exhorting you to contend earnestly for the faith which was once for all delivered to the saints."
Jude is exhorting believers to strenuously defend, as in a contest, the truth that they had received. Many believers know the LORD as their personal Savior, but they do not always know the privileges and promises that they have in Him and how to receive them. Could it be that many believers do not have a solid foundation of Gods Word in their hearts? Could this be due to Satan coming immediately and takes away the word that was sown in their hearts? Let's face it, faith grows through the very things that the devil comes to steal from the hearts of believers.
So then faith comes by hearing, and hearing by the word of God. (Romans 10:17)