The sin of killing one's mother

Original text of the first section of the Upāsaka Five Precepts Sūtra: 若居士作方便欲杀母。而杀非母。是中罪可悔。若居士欲杀非母。而自杀母。是犯中罪可悔。非逆。若居士方便欲杀人。而杀非人。是中罪可悔。若居士作方便欲杀非人。而杀人者。犯小可悔罪。若人怀畜生胎。堕此胎者。犯小可悔罪。若畜生怀人胎者。堕此胎死者。犯不可悔。

Explanation: If an upāsaka adopts certain means intending to kill his own mother, but actually kills someone who is not his mother, he commits a middling offense that can be repented. This is because he had no intention to kill with respect to the one who was not his mother—it was a case of mistaken killing. If the person an upāsaka intends to kill is not his own mother, yet he ends up killing his own mother, he also commits a middling offense that can be repented; because he had no intention of killing his mother, he does not incur the five rebellious acts of killing his mother.

If an upāsaka devises certain expedient means intending to kill a human being, but ends up killing a non-human being instead, he commits a middling offense that can be repented, because the offense of killing a non-human being is lighter. If an upāsaka devises certain expedient means intending to kill a non-human being, but ends up killing a human being instead, he commits a minor offense that can be repented, because he had no intention of killing a human being—the human was killed by mistake, so the offense is lighter. If a human is pregnant with an animal fetus and aborts that fetus, he commits a minor offense that can be repented. If an animal is pregnant with a human fetus and that fetus dies from being aborted, the offense is beyond repentance, because this is equivalent to intentional killing of a human.

Original text: 若居士作杀人方便。居士先死。后若有死者。是罪犯可悔。若居士欲杀父母。心生疑。是父母非耶。若定知是父母杀者。是逆罪。不可悔。若居士生疑。是人非人。若心定知是人杀者。犯不可悔。

Explanation: If an upāsaka devises expedient means to kill a human being, but the upāsaka himself dies first, and afterwards someone else dies because of the expedient means he devised, the upāsaka commits an offense that can be repented. If an upāsaka intends to kill his father or mother but has doubts arise in his mind, uncertain whether the person is his parent or not—if he knows with certainty that it is his parent and kills him or her, he commits one of the five rebellious acts, which is beyond repentance. If an upāsaka has doubts arise in his mind, uncertain whether the person is a human or a non-human being—if he knows with certainty in his mind that the person is a human and kills him, he commits an offense that is beyond repentance.