Strength: A messenger carries out his mission.
The point of the outcome is that a messenger fulfills his mission. The accepted position is that a messenger will strive to fulfill his duties as a messenger in a successful manner.
("Rav Yehiel said: A messenger who carries out his mission. Rav Nachman said: According to the Torah, there is no messenger who carries out his mission. According to the scribes, a messenger who carries out his mission. And Rav Sheshet said: One of these and one of these - a messenger who carries out his mission" - Erubin, not cited in the second edition)
Translation
Expression (Hebrew)
חֲזָקָה: שָׁלִיחַ עוֹשֶׂה שְׁלִיחוּתוֹ
Definition (Hebrew)
נְקֻודַּת הַמּוֹצָא הִיא כִּי שָׁלִיחַ מְבַצֵּעַ אֶת שְׁלִיחוּתוֹ. הַנָּחָה מְקֻבֶּלֶת הִיא כִּי שָׁלִיחַ יִתְאַמֵּץ לְמַלֵּא אֶת תַּפְקִידוֹ כְּשָׁלִיחַ בְּצוּרָה מֻצְלַחַת.
("אָמַר רַב יְחִיאֵל: חֲזָקָה- שָׁלִיחַ עוֹשֶׂה שְׁלִיחוּתוֹ. אָמַר רַב נַחְמָן: בְּשֶׁל תּוֹרָה- אֵין חֲזָקָה שָׁלִיחַ עוֹשֶׂה שְׁלִיחוּתוֹ בְּשֶׁל סוֹפְרִים- חֲזָקָה, שָׁלִיחַ עוֹשֶׂה שְׁלִיחוּתוֹ. וְרַב שֵׁשֶׁת אָמַר: אֶחָד זֶה וְאֶחָד זֶה - חֲזָקָה, שָׁלִיחַ עוֹשֶׂה שְׁלִיחוּתוֹ"- עֵרוּבִין לֹא ע"ב)