כַּאֲשֶׁ֨ר הָיָ֤ה יְהוָה֙ עִם־אֲדֹנִ֣י הַמֶּ֔לֶךְ כֵּ֖ן יהי [יִֽהְיֶ֣ה] עִם־שְׁלֹמֹ֑ה וִֽיגַדֵּל֙ אֶת־כִּסְא֔וֹ מִ֨כִּסֵּ֔א אֲדֹנִ֖י הַמֶּ֥לֶךְ דָּוִֽד׃
So wie Gott mit meinem Herrn, dem König, war, so sei er mit Salomo, und erhöhe seinen Thron noch über den Thron meines Herrn, des Königs Davids.
Rashi
Than the throne of my lord Dovid Hamelech. From this [we derive] that a father is not envious of his son.30See Maseches Sanhedrin 105b.
Ralbag
and make his throne greater than the throne of my lord King David: We learn from this that this is not with respect to the kingship, but this is that the will of the king is for his son to succeed even more than him.