But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth. (Acts 1:8)
Acts 1:8 and Hebrews 12:1 both translate the Greek word mártus as “witnesses.” In Acts 1:8 the sense is that of someone who bears witness to an event, while in Hebrews 12:1 the sense seems to be that of spectators observing an event. Taking the apparent sense of Acts 1:8, a witness is someone who would testifies before a court trial and provides an eyewitness account, or some other form of evidence used to substantiate the facts of an event. However, in Hebrews 12:1, the sense seems to be that of a crowd observing a sports event and cheering on their favorite team. Considering that “witnesses” is translating the same Greek word in both Acts 1:8 and Hebrews 12:1, how do we reconcile the apparent discrepancy?
The word “witness” or “witnesses” is used extensively throughout the N.T. and also in the O.T. The word “witness” or “witnesses” appears 184 times in the King James Bible (KJV): 87 times in the O.T. and 97 times in the N.T. Seventy-one times in the O.T. the KJV translates the Hebrew (Strong’s OT 5707) `ed; contracted from OT: 5749 concretely, a witness; abstractly, testimony; specifically, a recorder, i.e. prince: KJV – witness. Isaiah 33:8 translates `ed as “the cities”: “The highways lie waste, the wayfaring man ceaseth: he hath broken the covenant, he hath despised the cities, he regardeth no man” (emphasis added). Here, it is “the cities” that are “the record” or “the witness” to a broken covenant, but in every other appearance the word is simply translated “witness” or “witnesses.” Four times the KJV translates the Hebrew(Strong’s OT 5749) `uwd (ood); a primitive root; to duplicate or repeat; by implication, to protest, testify (as by reiteration); intensively, to encompass, restore (as a sort of reduplication): KJV – admonish, charge, earnestly, lift up, protest, call (take) to record, relieve, rob, solemnly, stand upright, testify, give warning, (bear, call to, give, take to) witness. This word appears 44 times in the O.T. and is translated in several different ways, but always with the sense of bearing witness to something.
In the N.T., mártus appears 35 times: three times it is translated as “martyr” (Acts 22:20; Revelation 2:13; 17:6) and twice it is translated as “record” (2 Corinthians 1:23; Philippians 1:8). Otherwise it is simply translated as “witness.” Strong’s defines mártus [Strong’s NT 3144]: of uncertain affinity; a witness (literally [judicially] or figuratively [genitive case]); by analogy, a “martyr”: KJV – martyr, record, witness. The verb form of the word, marturéo [Strong’s NT 3140], means: to be witness, i.e. testify (literally or figuratively): KJV – charge, give [evidence], bear record, have (obtain, of) good (honest) report, be well reported of, testify, give (have) testimony, (be, bear, give, obtain) witness.
Both the O.T. and the N.T. favor the sense that a witness is someone or something that gives testimony or evidence to a fact. In Acts 1:8 Jesus said: “ye shall be witnesses unto me both in Jerusalem …” In other words, “go bear testimony of Me. If someone asks you about Me, give them the factual record of Me. You may even have to die for your testimony.”
Hebrews 12:1 seems to present a different picture: “Wherefore seeing we also are compassed about with so great a cloud of witnesses.” From the English construction, it appears that the witnesses are spectators to an event. Indeed, Robertson says: “An old word (Latin: nubes), here only in the New Testament, for vast mass of clouds. Nefelee is a single cloud. The metaphor refers to the great amphitheater with the arena for the runners and the tiers upon tiers of seats rising up like a cloud.” However, he elaborates: “The martures here are not mere (emphasis mine) spectators [theatai ), but testifiers (witnesses) who testify from their own experience (Heb 11:2,4-5,33,39) to God’s fulfilling his promises as shown in Heb 11.” But is Hebrews 12:1 referring to the “witnesses” or to their “witness,” i.e., their “testimony”? The USB New Testament Handbook seems to agree with Roberson: “The thought is that the Old Testament heroes are watching how the writer of Hebrews and his readers ‘run their race’ in the Christian life, since their own salvation is linked with that of Christians (Heb 11:40). This large crowd of witnesses consists of the heroes of faith recorded in chapter 11.” Wuest offers an alternative view: “Rather than seeing the witnesses as spectators looking at this earthly scene from heaven, it would seem nearer the correct interpretation here to think of these first century readers running their Christian race, not having in mind the witnesses of 11:4-40 as spectators, but rather their testimony as examples urging them on to faith in Messiah as High Priest.”
The “Wherefore” (therefore) that begins this verse alerts the reader that what follows must be taken in context with what came before, i.e., “The Faith Hall of Fame.” Because of these examples of faith – these “witnesses,” these “testimonies” – we are to “run with patience the race that is set before us.” The examples are an enormous cloud on which we can lay hold. “Are compassed about” translates the Greek échontes perikemeínon. The first word, échontes, is a present, active, participle meaning to “have, hold, wear, be able or consider.” The active voice indicates that the subject (we) is performing the action. This indicates that we “have” or we “hold” this “great cloud of witnesses.” The second word, perikemeínon, is a present, middle, participle meaning to “be around, surround or wear.” The middle voice suggests that the subject acts in relation to himself. Together the translation could be rendered: “We hold around ourselves so great a cloud of witnesses.” Since it is impractical to think that we are holding on to saints that have gone on before, it makes more sense that we hold around ourselves their testimonies of faith. These are the witnesses of Hebrews 12:1! “The noun witness, even where it has the idea of looking on, anticipates bearing witness later to what had been seen earlier. The heroes of Hebrews  attest to the fact that faith brings approval from God. Believers are surrounded by this O.T. host of witnesses. Because this is true, Christians are to run their race with endurance.”
Who or what are witnesses? The answer is both. Witnesses are those who testify or give witness to an event, and they are the testimonies or those things which bear witness to an event. In Acts 1:8 Jesus told His disciples, “ye shall be My witnesses” (note that there is no choice in the matter). In Hebrews 12:1 we are encouraged to persist in our witness as we lay hold of the great testimonies of those who have gone before us. This would not only include Bible saints, but the saints that are enduring the race along with us. Let us also remember that God has provided substantial “witnesses” in our own lives by the way He has guided us and provided for us individually in the past.
 Strong’s translations are copied from the Biblesoft’s New Exhaustive Strong’s Numbers and Concordance with Expanded Greek-Hebrew Dictionary, (Copyright © 1994, 2003, 2006 Biblesoft, Inc. and International Bible Translators, Inc.).
 From Robertson’s Word Pictures in the New Testament, (Electronic Database Copyright © 1997, 2003, 2005, 2006 by Biblesoft, Inc., Robertson’s Word Pictures in the New Testament, Copyright © 1985 by Broadman Press).
 From the UBS New Testament Handbook Series, (Copyright © 1961-1997, by United Bible Societies).
 From Wuest’s Word Studies from the Greek New Testament, (Copyright 1940-55 by Wm. B. Eerdmans Publishing Co., Copyrights © renewed 1968-73 by Jeannette I. Wuest).
 Toussaint, Stanley D., The Epistle to the Hebrews, class notes, Revised, Spring 2008, p. 32.