Genesis 49:3

“Reuben, thou art my firstborn, etc.] Jacob addressed himself to Reuben first, in the presence of his brethren, owned him as his firstborn, as he was, (<012931>Genesis 29:31,32) did not cashier him from his family, nor disinherit him, though he had greatly disobliged him, for which the birthright, and the privileges of it, were taken from him, (<130501>1 Chronicles 5:1,2) my might, and the beginning of my strength; begotten by him when in his full strength f1867, as well as the first of his family, in which his strength and glory lay; so the Septuagint, “the beginning of my children”; and because he was so, of right the double portion belonged to him, had he not forfeited it,…”

“- Jacob Blesses His Sons 5. מכרה mekêrāh, “weapon;” related: כיר kārar or כרה kārāh dig. “Device, design?” related: מכר mākar “sell,” in Arabic “take counsel. Habitation.” 10. מחקק mechoqēq, “lawgiver, judge, dispenser of laws.” This word occurs in six other places - Numbers 21:18; Deuteronomy 33:21; Jud. Deuteronomy 5:14; Psalms 60:9; Psalms 108:9; Isaiah 33:22; in five of which it clearly denotes ruler, or judge. The meaning “sceptre” is therefore doubtful. שׁילה shı̂ylôh, Shiloh, a softened form of שׁילון shı̂ylôn, a derivative of שׁל shol, the ultimate root of שׁלה shālâh, שׁלם shālam, and possibly שׁלט shālaṭ, and hence, denoting “the peacemaker, the prince of peace.” It…”

“49:3-4 As firstborn, Reuben was entitled to be head of the family, but because he had the ungoverned impulses of boiling or turbulent waters (35:22), Jacob prophesied that Reuben would fail in leadership (see 37:21-22, 29; 42:22, 37-38; cp. Judg 5:15-16; 1 Chr 5:1-2).”