וַיִּקַּח֩ צֶ֨מֶד בָּקָ֜ר וַֽיְנַתְּחֵ֗הוּ וַיְשַׁלַּ֞ח בְּכָל־גְּב֣וּל יִשְׂרָאֵל֮ בְּיַ֣ד הַמַּלְאָכִ֣ים ׀ לֵאמֹר֒ אֲשֶׁר֩ אֵינֶ֨נּוּ יֹצֵ֜א אַחֲרֵ֤י שָׁאוּל֙ וְאַחַ֣ר שְׁמוּאֵ֔ל כֹּ֥ה יֵעָשֶׂ֖ה לִבְקָר֑וֹ וַיִּפֹּ֤ל פַּֽחַד־יְהוָה֙ עַל־הָעָ֔ם וַיֵּצְא֖וּ כְּאִ֥ישׁ אֶחָֽד׃
און ער האָט גענומען אַ געשפּאַן רינדער, און האָט זײ צעשניטן, און פֿאַנאַנדערגעשיקט דורך דער האַנט פֿון די שלוחים אין גאַנצן געמאַרק פֿון ישׂראל, אַזױ צו זאָגן: װער עס גײט ניט אַרױס נאָך שָאולן און נאָך שמואלן, װעט אַזױ געטאָן װערן צו זײַנע רינדער. איז אַ פּחד פֿון גאָט געפֿאַלן אױפֿן פֿאָלק, און זײ זײַנען אַרױס אַזױ װי אײן מאַן.
Bekhor Shor
To cause you to cross over in the covenant All of you are ready to cross into the covenant, and all of you are together. And for this it's good to execute the commandment now, that not one of you is able to say: I was not in the covenant, and did not accept the covenant upon myself. Since when you will cross the Yarden and be scattered each man to his inheritance and portion, it will be impossible to gather all of you together as you are now - since it's impossible that there will be no birthing woman or sick person or person kept aaginst their will, or lame person, and it's impossible to leave the houses and cities without any creature. But now, behold all of you are in one area and one camp, and all of you hear and see the execution of the covenant, and not one of you is able to withdraw and say 'I was not in the covenant'. "Execution [lit. "cutting" כריתות] of the covenenant" since they cut the calf into two, and "to cause you to cross over" since they passed between the parts of the calf that Avraham our father did between the parts, as it says "and divided them in the midst" (Bereishit 15:10). And like they did when they executed the covenant to send the slaves free (Yirmiyahu 34:13), the calf which was cut into two and they passed between the parts, this is a sign that when you pass over the covenant this is how it will be cut. Like, "And Shmuel took one milk-goat" (I Samuel 7:9), "And Tzamad took a cow and cut it into parts" (I Samuel 11:7) -- to say, which will not go after Shaul and after Shmuel, so will be done to his cow.
Rashi
מפדן ארם FROM PADAN-ARAM — Because there were two Arams — Aram-Naharaim (Mesopotamia) and Aram-Zoba — it is called Padan-aram, (Padan meaning pair). It has the same meaning as צמד in the phrase צמד בקר (Samuel 11:7) which we know signifies a pair of oxen and which is translated in the Targum by פדן תורין a Padan of oxen, so that we see that Padan means a pair. Some, however, explain Padan-aram to be the same as (Hosea 12:13) “the field (country) of Aram”, because in the Arabic language a field is called Padan.