וַיַּ֤רְא רֵאשִׁית֙ ל֔וֹ כִּי־שָׁ֛ם חֶלְקַ֥ת מְחֹקֵ֖ק סָפ֑וּן וַיֵּתֵא֙ רָ֣אשֵׁי עָ֔ם צִדְקַ֤ת יְהוָה֙ עָשָׂ֔ה וּמִשְׁפָּטָ֖יו עִם־יִשְׂרָאֵֽל׃ (ס)
Ia memilih bagian yang pertama bagi dirinya, sebab di sanalah tersembunyi sebidang tanah sang pemberi hukum; ia maju di barisan terdepan bangsa itu, ia melaksanakan keadilan Yang Mahakekal dan hukum-hukum-Nya bersama Israel.”
Rashi
וירא ראשית לו AND HE SAW THE FIRST PART FOR HIMSELF — i.e. he saw good to take for himself territory in the land of Sihon and Og, the subjugation of which was the beginning (ראשית) of the conquest of the Land,
Chizkuni
וירא ראשית לו, “he chose a first part for himself.” Even though the Ammonites and Moabites dispute his territorial claims to its land, as is evident from Judges 11,13 and Yiftach rebutting their arguments. (Compare Rashi there) Another interpretation of this line: What is the meaning of the phrase: כי שם חלקת מחוקק צפון, “for in part of that land the grave of the Israelites’ lawgiver (Moses would be hidden)" Alternately, Reuven has been referred to as the lawgiver; in Judges 5,15, when Deborah describes him as such with the words: בפלגות ראובן גדולים חקקי לב, “among the clans of Reuven who were debating great decisions of the heart.” The Reuvenites had long been entrenched in these lands already, (at the time of Yiftach, 300 years after Moses had died). According to yet another interpretation the whole line speaks about both Reuven and Gad, the two tribes who had decided to settle on the east bank of the Jordan river. Since both of these tribes had proven outstandingly strong, Moses accords them recognition already in his parting words to the people.
Da'at Zekenim
וירא ראשית לו, “he chose a first part for himself;” (the tribe of Gad) he chose the first part of the available land of Canaan for himself.” This is a reference to the lands formerly owned by the kingdom of Sichon and the kingdom of Og, both on the east bank of the river Jordan.