וְהָיָ֤ה זַרְעֲךָ֙ כַּעֲפַ֣ר הָאָ֔רֶץ וּפָרַצְתָּ֛ יָ֥מָּה וָקֵ֖דְמָה וְצָפֹ֣נָה וָנֶ֑גְבָּה וְנִבְרֲכ֥וּ בְךָ֛ כָּל־מִשְׁפְּחֹ֥ת הָאֲדָמָ֖ה וּבְזַרְעֶֽךָ׃
Y será tu simiente como el polvo de la tierra, y te extenderás al occidente, y al oriente, y al aquilón, y al mediodía; y todas las familias de la tierra serán benditas en ti y en tu simiente.
Rashi
ופרצת means AND THOU SHALT BECOME STRONG, like (Exodus 1:12) “the more they became strong".
Rashbam
ונברכו, an expression meaning “refining and improving thereby.” It means that these nations will be improved through intermarriage with your family. כל משפחות האדמה. The word is in a passive, weak mode as I have already explained on the same phrasing in Genesis 12,3
Kli Yakar
“And your descendants shall be like the dust of the earth, and you shall spread out.” The text should have said “and they shall spread out” [using plural form]. This alludes to what our Sages said in the Midrash (Lamentations Rabbah 2:7): When hardship comes, only Jacob feels it, as it is said He burned in Jacob like a flaming fire (Lamentations 2:3). And when good comes, only Jacob feels it, as it is said When the Lord restores the fortunes of His people, Jacob will rejoice and Israel will be glad (Psalms 14:7). Therefore it says and you shall spread out [in singular form], because since Jacob alone feels their good fortune, it appears as though he alone is the one who spreads out.