For if that first covenant had been faultless, then should no place have been sought for the second. If that first had been faultless - This is nearly the same argument with that in Hebrews 7:11. The simple meaning is: If the first covenant had made a provision for and actually conferred pardon and purity, and given a title to eternal life, then there could have been no need for a second; but the first covenant did not give these things, therefore a second was necessary; and the covenant that gives these things is the Christian covenant.
Related Commentaries of Hebrews 8:7
Hebrews 8:7
7 For if that first covenant had been faultless, then should no place have been sought for the second.