Talmud for Shevuot 4:1
שְׁבוּעַת הָעֵדוּת נוֹהֶגֶת בַּאֲנָשִׁים וְלֹא בְנָשִׁים, בִּרְחוֹקִין וְלֹא בִקְרוֹבִין, בִּכְשֵׁרִים וְלֹא בִפְסוּלִין. וְאֵינָהּ נוֹהֶגֶת אֶלָּא בָרְאוּיִין לְהָעִיד, בִּפְנֵי בֵית דִּין וְשֶׁלֹּא בִּפְנֵי בֵית דִּין, מִפִּי עַצְמוֹ, וּמִפִּי אֲחֵרִים, אֵין חַיָּבִין עַד שֶׁיִּכְפְּרוּ בָהֶן בְּבֵית דִּין, דִּבְרֵי רַבִּי מֵאִיר. וַחֲכָמִים אוֹמְרִים, בֵּין מִפִּי עַצְמוֹ וּבֵין מִפִּי אֲחֵרִים, אֵינָן חַיָּבִין עַד שֶׁיִּכְפְּרוּ בָהֶן בְּבֵית דִּין:
The oath of testimony obtains with men, and not with women, [it being written (Leviticus 5:1): "and he is a witness." Scripture speaks of one who is fit to testify, and a woman is not fit to testify, it being written (Deuteronomy 19:17): "Then the two men shall stand" — men and not women. And that verse speaks of witnesses, it being written there: "two," and elsewhere (Ibid. 14): "By word of two witnesses."], with non-kin, and not with kin, [kin being unfit to testify, it being written (Ibid. 24:16): "Fathers shall not be put to death by sons" — by the testimony of sons. And the same applies to the other kin.], with those who are kasher, and not with those who are pasul ("rejected"), [such as those liable to the death penalty, those liable to stripes, and robbers, these being called "evildoers," and the Torah writing (Exodus 23:1): "Do not make an evildoer a witness."] And it obtains only with those who are fit to testify, [to exclude a king, who does not testify, and those who are unfit to testify by rabbinic ordinance, such as gamblers and pigeon racers.], before beth-din and not before beth-din by his own mouth [i.e., If he himself says "I swear that I know of no testimony for you," he is liable, whether he swore before beth-din or not before them.] And (if besworn) by others, they are not liable unless they deny (possessing testimony) in beth-din. [e.g., If one says to them: "I beswear you to come and testify for me," and they say: "We know of no testimony for you," they are not liable unless they deny it in beth-din, it being written (Leviticus 5:1): "If he does not know, he shall bear his sin" — in a place (beth-din), where if he told, it would avail. And the verse speaks of one who is besworn by others.] These are the words of R. Meir. [The halachah is not in accordance with R. Meir.] The sages say: whether swearing by himself or besworn by others, they are not liable unless they deny it in beth-din.