וַיַּ֤רְא רֵאשִׁית֙ ל֔וֹ כִּי־שָׁ֛ם חֶלְקַ֥ת מְחֹקֵ֖ק סָפ֑וּן וַיֵּתֵא֙ רָ֣אשֵׁי עָ֔ם צִדְקַ֤ת יְהוָה֙ עָשָׂ֔ה וּמִשְׁפָּטָ֖יו עִם־יִשְׂרָאֵֽל׃ (ס)
E scelse una prima parte per se stesso, poiché lì una parte di un sovrano era riservata; E vennero i capi del popolo, eseguì la giustizia dell'Eterno e le sue ordinanze con Israele. .
Shenei Luchot HaBerit
ויתא ראשי עם צדקת ה' עשה ומשפטיו עם ישראל . I have heard a commentary according to which the tribe of Gad is praised for having conducted itself with more than the required amount of piety not only by marching with the other tribes in the war of conquest under the leadership of Joshua, but also by being in the vanguard. According to the agreement made with Moses In Numbers chapter 32 all that was required of this tribe was to put every able-bodied man under the joint command. This is why Moses says: ומשפטיו עם ישראל, "according to the law agreed with him he had to go with Israel." Gad, however, did more than was required, hence Moses mentions his צדקה, his righteousness.
Shenei Luchot HaBerit
This is also why Moses in his blessing of the tribe of Gad in Deut. 33,21 refers to that tribe as having performed צדקת ה' עשה ומשפטיו עם ישראל, "both a deed of righteousness vis-a-vis G–d and one of justice did he (the tribe) perform with Israel." From a legal point of view the tribe of Gad did only have to take part in the conquest of the land, something which took seven years. The additional seven years that were required to parcel out the land was an act of צדקה, something volunteered. By honoring this voluntary undertaking, the tribe qualified for Moses' unstinting praise. The Torah wishes us to apply such modes of behavior not only when it concerns utterances that may be financially costly for us, but also when such utterances imply undertakings by our souls, i.e. our religious conduct.
Shenei Luchot HaBerit
Aaron alluded to this when he told Moses who was about to bring his wife and children to Egypt, על הראשונים אנו מצטערים ואתא בא להוסיף, that it was sad enough that Israel found itself enslaved and tortured on account of a minor sin of Abraham. Why did Moses want to bring his sons to share the people's misery? The people referred to as having the משפטים set before them, i.e. the judges, are therefore added (ואלה) to the group that had been called ראשית, i.e. superior people, qualifying for being judged by the attribute of Justice. Moses himself would be viewed as ראשית הראשונים, the first of the elite.