Will the Holy Spirit ever lead a believer to do something contrary to the law?
No. The Holy Spirit will never lead a believer to do anything contrary to the law. He will not lead someone into adultery or idolatry. Instead, under grace, the Holy Spirit leads, guides, and directs believers so that they keep the law, though under a different set of circumstances than the oldness of the letter.
Les teaches that Paul can write as a Jew about serving in newness of spirit and not in the oldness of the letter. The believer is no longer under the demands of the Ten Commandments of Moses but is now under the control of the Holy Spirit. Les then asks logically whether the Holy Spirit would ever lead a believer to do something contrary to the law, and answers, "No. Of course not." The Holy Spirit will never lead someone into adultery or idolatry. Without the burden of the law and the fear of breaking it, believers now have grace, and the Holy Spirit leads, guides, and directs them so that they keep the law, though under a whole different set of circumstances. Paul says all things are lawful because he is not under the law, but he will not be brought under the power of the things the law forbids.