when they

Numbers 4:15
When Aaron and his sons have finished covering the holy objects and all their equipment, as soon as the camp is ready to move, the Kohathites shall come and do the carrying. But they must not touch the holy objects, or they will die. These are the transportation duties of the Kohathites regarding the Tent of Meeting.

Numbers 7:9
But he did not give any to the Kohathites, since they were to carry on their shoulders the holy objects for which they were responsible.

Joshua 3:3
and commanded the people: "When you see the ark of the covenant of the LORD your God being carried by the Levitical priests, you are to set out from your positions and follow it.

1 Chronicles 15:2, 15, 25, 26
Then David said, "No one but the Levites may carry the ark of God, because the LORD has chosen them to carry the ark of the LORD and to minister before Him forever." . . .

oxen

1 Kings 8:5
There, before the ark, King Solomon and all the congregation of Israel who had assembled with him sacrificed so many sheep and oxen that they could not be counted or numbered.

2 Chronicles 5:6
There, before the ark, King Solomon and all the congregation of Israel who had assembled with him sacrificed so many sheep and oxen that they could not be counted or numbered.