Shevuos4: 9
,,מַשְׁבִּיעַ אֲנִי עֲלֵיכֶם, כְּשֶׁתֵּדְעוּן לִי עֵדוּת, שֶׁתָּבוֹאוּ וּתְעִידוּנִי” — הֲרֵי אֵלּוּ פְטוּרִים, מִפְּנֵי שֶׁקָּדְמָה שְׁבוּעָה לָעֵדוּת.
“I adjure you that, when you know testimony for me, that you will come and testify for me” —- they are exempt, because the oath preceded the testimony.
Shevuos4: 10
עָמַד בְּבֵית הַכְּנֶסֶת וְאָמַר: ,,מַשְׁבִּיעַ אֲנִי עֲלֵיכֶם, שֶׁאִם אַתֶּם יוֹדְעִים לִי עֵדוּת, שֶׁתָּבוֹאוּ וּתְעִידוּנִי” — הֲרֵי אֵלּוּ פְטוּרִין, עַד שֶׁיִּהְיֶה מִתְכַּוֵּן לָהֶם.
[If] he stood in the synagogue and said, `I adjure you that, if you know testimony for me, that you come and testify for me” —- they are exempt, unless he directs himself to them.