סימן ק סעיף כא
הָרַג אֶת הַנֶּפֶשׁ בְּמֵזִיד, אֲפִלּוּ עָשָׂה תְּשׁוּבָה, לֹא יִשָֹא אֶת כַּפָּיו. וְאִם הָרַג בִּשְׁגָגָה וְעָשָׂה תְשׁוּבָה, נוֹשֵׂא אֶת כַּפָּיו. וְכֵן מוּמָר שֶׁעָשָׂה תְשׁוּבָה, נוֹשֵׂא אֶת כַּפָּיו. נָשָׂא גְּרוּשָׁה אוֹ חֲלוּצָה אוֹ שֶׁנִּטְמָא לְמֵּת שֶׁאָסוּר לוֹ לִטְמָא אֵלָיו, לֹא יִשָּׂא אֶת כַּפָּיו, עַד שֶׁיַּעֲשֶׂה תְשׁוּבָה עַל פִּי תַּלְמִיד חָכָם. וּשְׁאָר עֲבֵרוֹת, אֵינָן מוֹנְעוֹת מִנְּשִׂיאַת כַּפָּיִם. חָלָל, אֵינוֹ נוֹשֵׂא אֶת כַּפָּיו.
A kohein, who once intentionally killed someone, even though he has repented, may not raise his hands to bless the people.55Peri Chadash, Eliyahu Rabbah. But the Ramah 128:35 permits him. Shulchan Aruch forbids him, even if it was accidental. Biyur Halachah remains undecided, but if he went up, he shouldn’t step down. If he accidentally killed someone, and has repented, he may raise his hands. Similarly, an apostate56An idol worshipper or one who publicly desecrates Shabbos may not go up to duchan. (Mishnah Berurah 128:134, see Igros Moshe 1:33) who repented, may raise his hands to bless the people. A kohein who married a divorcee, or a chalutzah57According to Deut. 25:5–10, a brother-in-law has the obligation to marry his brother’s childless widow. If he declines, he must perform the chalitzah ceremony, whereby the widow attains the status of chalutzah. A kohein is forbidden to marry a chalutzah or a divorcée., or who became ritually unclean by contact with a corpse,58Even a non-Jewish corpse, which is not a de’oraisa prohibition. (Mahari Assad 47) A kohein who is a medical student or doctor and exposes himself to this, may not duchan. (Ksav Sofer 16, Maharam Shick 303) This is only if he does this on purpose, but if by accident (out of ignorance), he may duchan. (Beis Yosef, Mishnah Berurah 128:150) for whom he is forbidden to defile himself, may not raise his hands until he repents under the direction of a Torah scholar. Other transgressions do not disqualify a kohein from raising his hands. A chalal59A chalal is a person born from a marriage forbidden only to kohanim. may not raise his hands to bless the people.60If he went up to the duchan, he must step down. (Peri Chadash)
תנא דבי אליהו כל השונה הלכות בכל יום מובטח לו שהוא בן העולם הבא שנאמר הליכות עולם לו אל תקרי הליכות אלא הלכות (נדה ע"ג.)