At this point in His ministry, Jesus tells them not to be concerned with procuring extra provisions for their journeys as they went to preach the gospel, heal the sick, and cast out demons. He specifically instructed them, "Take nothing for the journey, neither staffs nor bag nor bread nor money; and do not have two tunics apiece" (Luke 9:3). A short time later, He gave similar instructions: "Carry neither money bag, knapsack, nor sandals; and greet no one along the road" (Luke 10:4). The parallel account in Matthew 10:7-10 mirrors these directives:
And as you go, preach, saying, "The kingdom of heaven is at hand." Heal the sick, cleanse the lepers, raise the dead, cast out demons. Freely you have received, freely give. Provide neither gold nor silver nor copper in your money belts, nor bag for your journey, nor two tunics, nor sandals, nor staffs; for a worker is worthy of his food.
Jesus Christ was not issuing a blanket prohibition against sandals, or against money, or against owning more than one shirt. However, for a limited interval of time, He directed them to travel lightly, for a number of reasons.
First, for these initial activities, Christ did not want His disciples to be concerned about physical preparations. He wanted them to focus on the job that He had given them to do—preach the gospel and report back to Him—rather than on worrying about obtaining extra clothing or footwear. His emphasis was on the mission He was sending them on, but He knew human nature's tendency to worry about the details of its own comfort and existence. He did not want the disciples caught up in any preparations that would delay or distract them from His work through them.
Second, Christ was helping them to build faith in God as their Provider. He was teaching them to live and do His work without concern for their physical lives. He states clearly that if we are seeking His Kingdom first, and all that it entails, God will provide for all of our real needs (Matthew 6:33). The Father provides for even the birds and flowers, and we are of much greater worth than these (verses 25-32). God even has a name that reflects this: YHWH-Jireh, the Lord will provide as He thinks fit.
There is an alleged contradiction between the accounts given by Matthew and Mark. In Mark 6:8-9, Jesus says, "Take nothing for the journey except a staff—no bag, no bread, no copper in their money belts—but to wear sandals, and not to put on two tunics." In Matthew 10:9-10, He instructs, "Provide neither gold nor silver nor copper in your money belts, nor bag for your journey, nor two tunics, nor sandals, nor staffs." This problem is easily resolved when we realize that He is really talking about two different things. In Matthew's account, Jesus does not forbid wearing sandals or carrying a staff, but only forbids their providing themselves with more—getting extra ones. Instead of being concerned when their current trappings wore out, they should trust God to supply their need and go just as they were. On this verse Albert Barnes comments, "The meaning of the two evangelists may be thus expressed: 'Do not procure anything more for your journey than you have on. Go as you are, shod with sandals, without making any more preparation.'"
Third, Christ did not want His disciples caught up in the spirit of materialism. Certain elements within the culture of the day would "preach" for money, either religiously or philosophically. Charlatans would sell "snake oil" cures. Mediums and spiritists could do seemingly miraculous things—for a price. People in this society would do anything to turn a quick penny just like today.
Christ's words in Matthew 10:8 are meant to counteract this mindset. He had given the disciples miraculous power to heal and cleanse, as well as authority over demons. Yet, because He had given these spiritual gifts to them freely, Christ told them to carry out His instructions without seeking monetary or material compensation. God's workers are worthy of their hire but should not build personal fortunes through the services they render for Him. God is certainly generous, and provides for His servants as He sees fit, but He prohibits them from using His gifts for their own gain. He will bless them as it pleases Him!