Halakhah for Horayot 24:19

From the laws of the commandment is that which they, may their memory be blessed, said (Horayot 12b) that it is one [if it is] a high priest that was anointed by the anointing oil or with many clothes, and it is one [if it is] a high priest that is serving or a high priest who they appointed and he left [the service], and likewise a priest anointed for war - they are all commanded about the virgin and forbidden with the widow. And that which they said (Yevamot 58b) that even if he betrothed a minor and she became an adult while [in his domain] before the marriage, behold this one should not [marry her]. But if he did [marry her], he does not [divorce her]. And that which they said (Yevamot 59a) that he never marry two women together, as it is stated, "And he shall take a woman in her virginity" - specifically one woman, and not two. And that which they said (Yevamot 61a) that if he [married] a widow while he was still a common [priest] and became appointed as high priest, he does not [divorce] her. And even if he [only] betrothed her before he was appointed high priest, he [marries] her after he is appointed. And the rest of its details are in the sixth chapter of Yevamot and in [various] places of Ketuvot and Kiddushin (see Rambam, Laws of Forbidden Intercourse 17).