Mark's and Luke's use of the same Greek term prevents us from relying on the original words' meanings to explain this apparent contradiction. Logic seems to support Mark's statements, and we know that Luke would never have contradicted the apostles' words without risking his credibility. Under these circumstances, how can we explain the difference?
To avoid this problem, some translators have added an ‘s’ to Matthew's and Luke's versions. Although the meaning is preserved, this translation seems to betray the apostles' words. Moreover, these versions are not accepted by most commentators. The literal difference therefore persists.
We propose the following explanation: Mark quotes another conversation on the same subject between the Teacher and the apostles. This is unsurprising, since they probably did not understand the first formulation: take neither money nor sandals nor a staff. It seems clear that they asked Jesus the Messiah what these words meant: must we go barefoot? Must we travel without a staff?
We observe the same principle in the conversation with Nicodemus: Jesus the Messiah makes a statement that seems difficult to understand. His listener then asks for clarification, and Jesus the Messiah explains his thought more precisely.
Jesus the Messiah therefore clarified his thought in his reply, the one we read in Mark: of course, take your sandals, those already on your feet, but take no spare pair; naturally take your staff, the one you usually use, but only that one. We find the following meaning: do not burden yourselves with belongings, but take the bare minimum. Do not waste time preparing for the journey; go as you are and concentrate solely on spreading the Gospel. Material needs must not limit you; they will be met by the new converts.
This attitude seems new, since journeys usually involved considerable logistical arrangements, with accompanying people who managed material matters.
Furthermore, Luke 22.35-36 offers a conclusion. Jesus the Messiah makes clear that he sent his disciples without money, a bag and, above all, shoes. He asks whether they lacked anything, and the disciples answer no! It seems obvious that, by saying without shoes, Luke means without spare shoes, since these men did not walk barefoot!
There is therefore no contradiction between Matthew's and Luke's words and those of Mark.