Rashi on Numbers 7:10/רש"י על במדבר ז׳:י׳

1ויקריבו הנשאים את חנכת המזבח AND THE PRINCES OFFERED FOR DEDICATING THE ALTAR — After they had presented the waggons and the oxen for carrying the Tabernacle, their heart prompted them to present offerings for the altar, in order to dedicate it (Here, ויקריבו denotes: they offered sacrifice).

2ויקריבו הנשיאם את קרבנם לפני המזבח AND THE PRINCES BROUGHT THEIR OFFERING BEFORE THE ALTAR, because Moses would not accept them at their hands until he was so bidden by the mouth of the Almighty (Sifrei Bamidbar 47).