וְאֶת־אֲחִיכֶ֤ם הַקָּטֹן֙ תָּבִ֣יאוּ אֵלַ֔י וְיֵאָמְנ֥וּ דִבְרֵיכֶ֖ם וְלֹ֣א תָמ֑וּתוּ וַיַּעֲשׂוּ־כֵֽן׃
Pero habéis de traerme á vuestro hermano menor, y serán verificadas vuestras palabras, y no moriréis. Y ellos lo hicieron así.
Rashi
ויאמנו דבריכם— means so shall your words be verified and confirmed. Other examples are, (Numbers 5:22) “It is true, it is true (אמן אמן)”, and (1 Kings 8:26) “Let thy word, I pray thee, be verified (יאמן).”
Chizkuni
.ויעשו כן, “they did so.” They agreed with Joseph’s conditions.
Sforno
ולא תמותו, he meant that they would not die here, as he was able to have them killed also in the land of Canaan if they would not come back of their own free will.