Mat 10:9-10 NASB20
"Do not acquire gold, or silver, or copper for your money belts, or a bag for your journey, or even two tunics, or sandals, or a staff; for the worker is deserving of his support.

Mar 6:8 NASB20
and He instructed them that they were to take nothing for their journey, except a mere staff--no bread, no bag, no money in their belt--but to wear sandals; and He added, “Do not wear two tunics.”

Luk 9:3 NASB20
And He said to them, "Take nothing for your journey, neither a staff, nor a bag, nor bread, nor money; and do not [even] have two tunics.

Solution proposed by Grant Osborne:
My solution is that Jesus sent them on more than one mission. [In] Matthew and Luke ..., ... the disciples' mission is sacred; Jesus therefore used a temple motif, according to which staff and sandals are left at the door because it is holy ground (see also the burning bush in Exodus 3:5). Mark ... narrated a different mission that Jesus views as a new exodus like Israel's in Exodus 12:11 when the people were told to eat the Passover meal in haste, with staff in hand and sandals on one's feet. Here in Luke we are to reflect on the sacredness of the mission on which Christ is sending his followers.

A possible support for this solution may be that in Matthew the twelve were sent only to the "lost sheep of the house of Israel" (Matt 10:5-6), however there is no mention of where to go in Mark or Luke.

See:
Ward on Words
Staff or no staff: the worst Bible “contradiction”
STAFF OR NO STAFF?
https://hermeneutics.stackexchange.com/questions/20497/harmonizing-matthew-1010-luke-93-mark-68