Jerusalem Talmud Shevuot 4:8

משנה: אָמַר לִשְׁנַיִם מַשְׁבִּיעַ אֲנִי עֲלֵיכֶם אִישׁ פְּלוֹנִי וּפְלוֹנִי שֶׁאִם אַתֶּם יוֹדְעִין לִי עֵדוּת שֶׁתָּבוֹאוּ וּתְעִידוּנִי וְהֵם שֶׁיּוֹדְעִין לוֹ עֵדוּת עֵד מִפִּי עֵד אוֹ שֶׁהָיָה אֶחָד מֵהֶן קָרוֹב אוֹ פָסוּל הֲרֵי אֵילּוּ פְטוּרִין׃ MISHNAH: If he said to two persons, I am putting an oath on you, X and Y, that you shall come and testify for me if you know testimony for me, but they knew from another witness¹⁰¹This is hearsay evidence inadmissible in court. If one of a group of witnesses is disqualified, the other one at most could force the defendant to swear; he never could force him to pay money. Therefore the oath is invalid also for the party which would be qualified., or one of them was a relative or disqualified. These are not liable.

הלכה: אָמַר לִשְׁנַיִם מַשְׁבִּיעַ אֲנִי עֲלֵיכֶם כול׳. רִבִּי מָנָא שָׁמַע מִדְּבַתְרֵיהּ אוֹ שֶׁהָיָה אֶחָד מֵהֶן קָרוֹב אוֹ פָסוּל. הָא לֹא הָיָה אֶחָד מֵהֶן קָרוֹב אוֹ פָסוּל חַייָבִין. וְיוֹדֵעַ הוּא בְהוֹן. הֲוֵי לֵית טַעֲמָא אֶלָּא מִשּׁוּם שֶׁאֵין מִתְכַּוֵּין לָהֶן. רִבִּי יוֹסֵי שָׁמַע לָהּ מִקַּדְמִיתָא. מִפְּנֵי שֶׁקָּדְמָה שְׁבוּעָה לָעֵדוּת׃ הָא לֹא קָֽדְמָה שְׁבוּעָה לָעֵדוּת חַייָבִין. וְיוֹדֵעַ הוּא בְהוֹן. הֲוֵי לֵית טַעֲמָא אֶלָּא מִשּׁוּם שֶׁאֵין מִתְכַּוֵּין לָהֶן. HALAKHAH: “If he said to two persons, I am putting an oath on you,” etc. Rebbi Mana understood it from the following, “or one of them was a relative or disqualified.” Therefore, unless one of them was a relative or disqualified, they are liable. And he knows who they are. Therefore the reason can only be that he does not intend them. Rebbi Yose understood it from the preceding, “since the oath preceded the testimony.” Therefore, if the oath did not precede the testimony, they are liable. And he knows who they are. Therefore the reason can only be that he does not intend them¹⁰²This again refers to Mishnah 11, it is a continuation of the preceding Halakhah. All the Mishnaiot quoted presuppose that the claimant knows exactly whom he wants as witness; nevertheless his imprecation is ineffective. Therefore it may be assumed that also in the case of Mishnah 11 it would be ineffective even if he knew exactly whom he intended..