Notice how Paul is teaching faith to the Hebrews but law to the Corinthians using the same example of the Israelites in the wilderness? Is Paul teaching Grace only? No, the Lord Jesus teaches law and faith and so does the apostles.
1 Corinthians 10:5 But with many of them God was not well pleased: for they were overthrown in the wilderness.
6 Now these things were our examples, to the intent we should not lust after evil things, as they also lusted. 7 Neither be ye idolaters, as were some of them; as it is written, The people sat down to eat and drink, and rose up to play. 8 Neither let us commit fornication, as some of them committed, and fell in one day three and twenty thousand. 9 Neither let us tempt Christ, as some of them also tempted[/B], and were destroyed of serpents. 10 Neither murmur ye, as some of them also murmured, and were destroyed of the destroyer. 11 Now all these things happened unto them for ensamples: and they are written for our admonition, upon whom the ends of the world are come. 12 Wherefore let him that thinketh he standeth take heed lest he fall. 13 There hath no temptation taken you but such as is common to man: but God is faithful, who will not suffer you to be tempted above that ye are able; but will with the temptation also make a way to escape, that ye may be able to bear it. 14 Wherefore, my dearly beloved, flee from idolatry.
Hebrews 3:7 Wherefore (as the Holy Ghost saith, To day if ye will hear his voice, 8 Harden not your hearts, as in the provocation, in the day of temptation in the wilderness: 9 When your fathers tempted me, proved me, and saw my works forty years. 10 Wherefore I was grieved with that generation, and said, They do alway err in their heart; and they have not known my ways. 11 So I sware in my wrath, They shall not enter into my rest.) 12 Take heed, brethren, lest there be in any of you an evil heart of unbelief, in departing from the living God. 13 But exhort one another daily, while it is called To day; lest any of you be hardened through the deceitfulness of sin. 14 For we are made partakers of Christ, if we hold the beginning of our confidence stedfast unto the end; 15 While it is said, To day if ye will hear his voice, harden not your hearts, as in the provocation. 16 For some, when they had heard, did provoke: howbeit not all that came out of Egypt by Moses. 17 But with whom was he grieved forty years? was it not with them that had sinned, whose carcases fell in the wilderness? 18 And to whom sware he that they should not enter into his rest, but to them that believed not? 19 So we see that they could not enter in because of unbelief.