"You have heard that it was said, ‘You shall not commit adultery.’ But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart. If your right eye causes you to stumble, gouge it out and throw it away. It is better for you to lose one part of your body than for your whole body to be thrown into hell. And if your right hand causes you to stumble, cut it off and throw it away. It is better for you to lose one part of your body than for your whole body to go into hell."
Excuse me for butting in but, Jesus was not speaking about law vs. grace. As you can plainly see from the context that he mentions adultery prior to his statement. And so he is speaking about sin in general. That said, if Jesus were speaking literally, then all believers would have no body parts left. He also said "unless you eat my flesh and drink my blood you have no life in you." Do you think that is to be taken literally as well?
Jesus is speaking figuratively here, meaning to sever from our lives the willful sin that leads to condemning judgment in the lake of fire. I believe that this is similar to the letters to the seven churches where at the end of each letter he makes reference to "him who overcomes." Whatever sins is impeding our walk in Christ, cut it out! Overcome it! Better to get that sinful pleasure out of our lives, than to be condemned and thrown into hell.
If we confess our sins he is faith and just and will forgive us our sin and cleanse us of all unrighteousness and that without cutting anything off. - 1 John 1:9
Hope this was helpful
Blessings to you in Christ!