Halakhah su Geremia 46:78

If a man marries a woman, she checked herself, and then had sexual relations, and afterward when she wiped herself and he [wiped himself] blood was found on the witness (Note: meaning the rag or cloth with which she checks herself) of hers or on his witness, and this occurred three consecutive times, she is forbidden to remain with her husband, and she is divorced without receiving ketuba monies, not the basic money nor the additional money, nor conditioned [moneys] from the conditions of the ketuba, for she is not capable of sexual relations. He divorces her and may never remarry her. What are the circumstances? When this occurs from the beginning of her marriage, and she saw blood with the first intercourse. But if this occurred afterward, then his field has been washed away (Note: meaning, from the verse, "why have your brave men been washed away," (Jeremiah 46:15), in other words, she has been damaged and lost by his bad luck). Therefore, if they had relations one time and did not find blood, and afterward she returned to seeing blood with every intercourse, he divorces her but must pay the entire ketuba, and may never remarry her. Note: Some authorities say that if he does not wish to marry another, and desires to stay with this woman at the hands (in the company) of a chaperone for one year, and he will not go to her except with witnesses, he is not required to divorce her (Beit Yosef in the name of Response Ram, and likewise in Responsa Rashba chapter 860). And certainly if she committed adultery, such that she becomes disgusting to him, it is permitted (to stay with her) in this manner (ibid.).

When a person comes to convert, say to him, "What did you see that motivated you to come to convert? If you know that Israel, in this time, that the Jewish people are oppressed, eroded, (The words are from "Why is your strong one overthrown?" -Jer. 46:15) insane, and suffering. If he says, I know this and I will still become a part of your people, receive him immediately and tell him the principles of the faith, that God is one and idol worship is forbidden, and tell him a lot about this, and teach him a few of the lighter mitzvot and a few of the more stringent mitzvot, and teach him about some of the punishments of the mitzvot, as it says, "Before you came to learn this, if you ate the forbidden fat, you would not be punished with excommunication, you transgressed Shabbat and you were not punished with stoning; but now, if you eat forbidden food, you will be punished with excommunication; and if you transgress Shabbat you will be punished with stoning." Don't say too much about this, and don't get too specific either. And when you teach him about the punishment of the mitzvot, also teach him about the rewards of the mitzvot and teach him that in the doing of certain mitzvot that will merit life in the world to come. There isn't a complete righteous person, rather a master of wisdom, that does the mitzvot and understands them. And say to him: "You should know that the world to come is hidden from the righteous, who are Israel. As for what you see that Israel is in distress in this world, because it is not granted them to receive the abundance of good things in this world like other peoples, lest their hearts should be indulged loftily and they should go astray and squander the reward of the world to come. But God didn't bring to them too much destruction, so that they would not observe. Rather, all of the idolators stand. And you explicate this idea so that he feels the dearness of it. If he receives this, circumcise him immediately and wait until he is fully healed, and afterwards, immerse him without a barrier. (Some say that you cut or shave his hair and you cut his fingernails and his toenails before immersion.) And three learned scholars stand at his back and teach him some of the light mitzvot and some of the more stringent mitzvot a second time, and he stands in the water. And if it is a woman, women sit her in the water up to her neck and the beit din is outside and they teach her some of the easy mitzvot and some of the more stringent mitzvot and she sits in the water and afterwards, she immerses before them and they turn their faces and leave in order that they do not see her when she is getting out of the water, and they bless the immersion after she comes out of the water. And once he has immersed, it is as if he is a Jew, but if he goes astray, he is like an apostate Jew - he is still sanctified, and his marriage is sanctified.