Mat 4:10 Begone, Satan! for it is written, 'You shall worship the Lord your God and him only shall you serve.'
Alternative: Off with you, adversary! for it is written, "You shall bow down to the Lord your God and you shall work for him above all others."
Unlike the previous two verses, it is hard to know exactly which verse in the OT Christ is referring to here. Some say Deu 6:13 (or similar quotes) but we would have to equate worship or more specifically bowing down in worship with "fear" and that doesn't seem like Christ's attitude toward the Father. The specific idea of worshiping and serving is most often stated in the negative: do not worship and serve other gods (example: Deu 11:16). Since the topic here is wealth, Isa 46:6 seems a good reference point. But in two previous tests, here and here, the quote Christ chose was followed by a references to himself, so this may refer to Psa 72:11, which refers to bowing down and serving and is the only such positive statement I can find with a clear references to the coming of a new age of the divine rule.
Christ tells us that our purpose in life is simply following God's plan for us. There is an interesting parallel here between worshiping our opponents and worshiping earthly wealth and power. Christ often casts status in society as one of our biggest enemies. His view is simple. Our testing is over when we come to realize that only God is worthy of homage and we should serve God above all others.
The challenge with obeying Christ's words here is knowing how we best serve God, that is, knowing what God's mission is for us personally. Christs three tests provide us a guide. First, we must seek our personal fulfillment by serving our spiritual needs rather than our physical needs. Second, we cannot expect any certainty or proof in divine matters. This leads us finally to simply honoring God by doing our best to serve Him.
It is interesting that this particular challenge is ties with the temptation of earthly power because it seems like those most willing to do evil in God's name are those who are seeking early power and more concerned with politics than with God. An interesting test for any person who claims to be representing God is seeing how actively they seek earthly wealth and power. By definition, such a person has failed the third test. Similarly a person that seeks physical gratification has failed the first test. A person who seeks proof and certainty in life fails the second test.
"Be gone" is from hupagô (hypago), which means "to lead under," "to bring under," "to bring a person before judgment," "to lead on by degrees," "to take away from beneath," "to withdraw," "to go away," "to retire," "to draw off," and "off with you."
"Satan" is satanas, (satanas) which is an Aramaic word meaning "adversary," "opponents," or "one who opposes another in purpose or act. " The word is used only in the New Testament. The meaning it has today as "the chief of evil spirits" comes from Christian traditions unknown at the time the Gospels were written. (More about satanas and demons here.)
"Wrote" is from graphô (grapho), which means "to write," "having marked or drawn," "to describe," "to brand," "to express by written characters," "to ordain," "to enroll oneself," "to be indicted," and "to write down."
"Worship" is from proskuneô (proskyneo), which means "make obeisance," "fall down and worship," and specifically means to prostrate yourself before authority, as we would use the Chinese term, "kowtow."
"Lord," is from kurios (kyrios), which means "having power," "being in authority" and "being in posession of." It also means "lord," "master of the house," and "head of the family."
"God" is from theos (theos), which means "God," the Deity."
"Only" is from monôs (monon), which means "alone," "solitary," "only," "one above all others," "made in one piece," "single," and "unique."
"Serve" is from latreuô (latreuo), which means "to work for hire or pay," "to be in servitude to," "to serve," "to be enslaved," and "to obey."