Is there a sin incurred merely by a very small part of the glans touching the anus, without full penetration or ejaculation?

If the act mentioned involves the wife, then the scholars have deemed it reprehensible to have intercourse with her between the buttocks, because it may lead to anal intercourse, which is forbidden. This reprehensibility increases to a state of obligation if there is a fear of falling into the prohibited act. If this happens unintentionally, without intending the forbidden, then it is hoped that there is no sin, while still requiring seeking forgiveness and resolving to abandon anything that leads to the forbidden. However, if the act was with a man, then it is a great evil and a serious crime that necessitates immediate and sincere repentance, one of the conditions of which is abandoning the sin and its cause.