Verily, the best of you are those who have the best moral conduct

The Prophet (may Allah's peace and blessings be upon him) was not the one to speak or act indecently, nor did he deliberately do that. Rather, he was one of exemplary good character. He said that the best believer is the one with the best manners and character. This is because good manners naturally lead to doing all what is good and shunning all what is bad.