The following is an excerpt from Dr. Thomas Holland's Crowned With Glory, ©2000, used with permission.
Mark 6:20 - "observed him"
"For Herod feared John, knowing that he was a just man and an holy, and observed him; and when he heard him, he did many things, and heard him gladly."
It is suggested that the phrase observed him is incorrect and should be translated kept him safe.  The problem is not with the translation, but with the lack of comprehending the English language. According to Webster's Third New International Dictionary, the word observe comes from the Latin word observare, which means to watch, guard, and observe.  This agrees with Dr. John C. Traupman's Latin Dictionary which defines observare as "to watch, watch out for, take careful note of; to guard; to observe, keep, obey, comply with; to pay attention to, pay respect to."  Further, the Oxford English Dictionary offers the definition of observe as, "To regard with attention; to watch; to watch over, look after." 
For the most part, we think of the word observe as meaning to watch, study, or take notice of. However, it also means to keep, protect, or preserve. For example, we speak of observing the speed limit. We do not mean that we are watching how fast we travel down the road; we mean we are obeying or keeping the law of the land. Some observe the Sabbath or a religious holiday. Again, this means they keep or respect the day. When the Coast Guard speaks of observing our shores, they are protecting them. So it is with forest rangers who set up observation posts for the purpose of protecting the wilderness. Both observe and preserve mean to keep something. This is why the same Greek word is used in Luke 2:19 and is translated as kept: "Mary kept all these things, and pondered them in her heart."
The Greek word is suntereo. In The Analytical Greek Lexicon this word is defined as "to observe strictly, or to secure from harm, protect."  James H. Moulton and George Milligan note that one of the uses of this word in ancient non-literary writings was when "a veteran claims that in view of his long military service, exemption from public burdens ought to be 'strictly observed' in his case."  Clearly either observe or kept safe are proper translations.
 James R. White, The King James Only Controversy: Can You Trust the Modern Translations? (Minneapolis: Bethany House, 1995), 224-225.
 Webster's Third New International Dictionary, Philip Babcock Gove, editor (Springfield Massachusetts: Merriam-Webster Inc., 1981), 1558.
 John C. Traupman, Latin Dictionary (New York: Amsco School Publications, 1966), 200.
 The Oxford English Dictionary 2nd edition, J.A. Simpson and E.S.C. Weiner, editors. (Oxford: Clarendon Press, 1989), 1196 (compact edition).
 Harold K. Moulton, The Analytical Greek Lexicon (Grand Rapids: Zondervan), 392.
 James H. Moulton and George Milligan, The Vocabulary Of The Greek Testament (Grand Rapids: Eerdmans, 1949), 614.