English Explanation of Mishnah Sanhedrin 3:5

A friend or an enemy [is disqualified]. “A friend”: this is one’s groomsman. “An enemy”: anyone whom he has not spoken to in three days because of anger.
They replied: “Israelites are not suspected of such.”
Mishnah five continues to discuss those people who are disqualified from testifying or acting as judges.
The first clause in the mishnah states that one may not testify or judge in a trial involving one’s friend or enemy. The next two clauses define the first clause. “A friend” who is disqualified from testifying or judging is a man’s groomsman, a person who helped him celebrate his wedding. “An enemy” is anyone with whom one has not spoken for three days due to anger.
It must be assumed that the first three clauses are a continuation of Rabbi Judah’s words, begun in the previous mishnah. The Sages in section 1d respond to Rabbi Judah by claiming that Jews are not suspected of lying in court because they are testifying with regards to a friend or enemy. Therefore, a person may testify and judge in cases involving a friend or an enemy.