Falling away means disassociating yourself

"Faith is being sure of what we hope for and certain of what we do not see" (Heb 11:1 NIV). "I know whom I have believed" (2Ti 1:12). "Each person must be fully convinced in his own mind" (Ro 14:5). "Our proud confidence is this: the testimony of our conscience . . . not in fleshly wisdom but in the grace of God" (2Co 1:12). "We are the true circumcision, who worship in the Spirit of God and glory in Christ Jesus and put no confidence in the flesh" (Php 3:3). "If anyone is confident in himself that he is Christ's, let him consider this again within himself, that just as he is Christ's, so also are we" (2Co 10:7). "If our heart does not condemn us, we have confidence before God" (1Jn 3:21). We are composed of body, soul and spirit and the heart is, spiritually speaking, connected with the last two whereby each person is "convinced in his own mind" (Ro 14:5). Accordingly Paul warns, "'Do not harden your hearts as when they provoked Me, as in the day of trial in the wilderness'" (Heb 3:8). "'They rebelled against Me and were not willing to listen to Me'" (Eze 20:8). "'Today, if you would hear His voice, do not harden your hearts'" (Heb 3:7) "as at Meribah, as in the day of Massah in the wilderness" (Ps 95:8). This can result in apostasy which is to reset your position by standing away from where you had previously associated yourself. "The Spirit explicitly says that in later times some will fall away from the faith" (1Ti 4:1) when "apostasy comes" (2Th 2:3). "In time of temptation [they] fall away" (Lk 8:13). "Nevertheless, the firm foundation of God stands, having this seal, 'The Lord knows those who are His'" (2Ti 2:19).

The author then quotes Psalm 95:7-11. In the first two chapters he quoted the Old Testament logically because he was appealing to Jews. He precedes this quote with, "Therefore, just as the Holy Spirit says" (Heb 3:7). "Therefore" signifies a conclusion. Also he is specifying God as this speaker as well as having written the psalm. Unbelief and rebellion are the subject. Consequences of this are emphasized with the parallel that "'they shall by no means see the land which I swore to their fathers, nor shall any of those who spurned Me see it'" (Nu 14:23). The wording of the Psalm 95:8-9 quote is a little different that Hebrews 3:8-9 but the content is the same. "'Do not harden your hearts as when they provoked Me, as in the day of trial in the wilderness'" (Heb 3:8). The psalm specifies "at Meribah, as in the day of Massah in the wilderness'" (Ps 95:8). The Greek word for "provoked" is dokimazo meaning to test with a view toward approval. It is associated with the geographical location Meribah which is called the place of strife. In the wilderness Israel stayed at Kadesh. "There was no water for the congregation . . . [and] the people thus contended with Moses" (Nu 20:2-3). God told Moses, "'Take the rod . . . and speak to the rock before their eyes, that it may yield its water'" (:8). "Then Moses lifted up his hand and struck the rock twice with his rod; and the water came forth abundantly" (:11). "He split the rocks in the wilderness and gave them abundant drink" (Ps 78:15). "Those were the waters of Meribah, because the sons of Israel contended with the Lord, and He proved Himself holy among them" (Nu 20:13).