Solid and verifiable evidence is an integral element of the divine justice. God insists on demonstrating and applying His own system of using physical, verifiable data to issue His judgment. Indeed, when He declares Himself as Just and an Advocate of justice, He sets for that the highest standards, based on solid proofs. Surely, the guided ones are the intelligent who recognize the truth within the confines of that system, based on proven facts. This conforms with their superior reasoning powers and resonates with their choice of living and leaving the earth in a state of true honesty, dignity and integrity.
A witness is one of the most powerful applications in God's justice system - in this life or on the Day of Judgment. God's first divine demonstration for the vitality of a witness is spelled out in 7:172. The service of being a witness is extensively highlighted in Quran that God swears by the witness and the witnessed (85:3). When God swears, He demands our utmost attention to the entities He swears by and to the content of His swearing.
[85:1] The sky and its galaxies.
[85:2] The promised day.
[85:3] The witness and the witnessed.
In this life, as learned from Quran, witnesses are mandatory solid proofs that certain transactions have been executed. They are also to establish evidence beyond doubt for certain accusations. The integrity of a witness is crucial to establish justice. When we reverence God alone and honestly serve our souls, we are committed to be truthful witnesses. When we are accustomed to lying, we are likely to cheat our souls and earn sins by bearing false witnesses. There are many disgraceful testimonies listed in Quran the disbelievers are held accountable for (6:19, 3:70,86,99).
The Day of Judgment is described by God as "the Day the witnesses are summoned", (40:51). This is an attribute of the Day of Judgment. On that day, the witness system continues to be a powerful application for God's divine justice that He insists to demonstrate so no one would claim lies or raise illegitimate arguments.
[40:51] Most assuredly, we will give victory to our messengers and to those who believe, both in this world and on the day the witnesses are summoned.
[28:75] We will select from every community a witness, then say, "Present your proof." They will realize then that all truth belongs with God, while the idols they had fabricated will abandon them.
Every single disbeliever (50:19,22) will have a witness to testify against his claims (50:21) on the Day of Judgment (50:20). This is what the following group of verses are stating. God assigns witnesses for those who persisted in denying His proofs as they will claim they did not receive any warnings or any guidance. Please note that a witness and a companion are distinct entities in Quran with distinct titles and qualities:
[50:19] Finally, the inevitable coma of death comes; this is what you tried to evade.
[50:20] The horn is blown; this is the promised day.
[50:21] Every soul comes with a herder and a witness.
[50:22] You used to be oblivious to this. We now remove your veil; today, your vision is (as strong as) steel.
[50:23] The companion said, "Here is my formidable testimony."
[50:24] Throw into Gehenna every stubborn disbeliever.
[50:25] Forbidder of charity, aggressor, full of doubt.
[50:26] He set up besides God another god. Throw him into severe retribution.
[50:27] His companion said, "Our Lord, I did not mislead him; he was far astray."
[50:28] He said, "Do not feud in front of Me; I have sufficiently warned you.
[50:29] "Nothing can be changed now. I am never unjust towards the people."
On that day, while some of the wicked jinn companions and humans will admit they have deviated and offer testimonies against themselves and/or their own companions (100:6-7, 6:130, 7:37, 41:20-21, 24:24), the duty of a witness is exclusive for the righteous.
[18:51] I never permitted them to witness the creation of the heavens and the earth, nor the creation of themselves. Nor do I permit the wicked to work in My kingdom.
Those who witness God and His message as we know from Quran are God Himself, the angels and the knowledgeable who believe in God alone as the only Lord and Master, including all His prophets and messengers (3:18). The angels along with Gabriel witnessed the revelation of Quran (4:166, 97:1-5). All these knowledgeable entities who witnessed God and His Truth will also serve God and His Truth as witnesses on the Day of Judgment:
[3:18] God bears witness that there is no god except He, and so do the angels and those who possess knowledge. Truthfully and equitably, He is the absolute god; there is no god but He, the Almighty, Most Wise.
[4:166] But God bears witness concerning what He has revealed to you; He has revealed it with His knowledge. And the angels bear witness as well, but God suffices as witness.
[78:38] The day will come when the Spirit and the angels will stand in a row. None will speak except those permitted by the Most Gracious, and they will utter only what is right.
[34:40] On the day when He summons them all, He will say to the angels, "Did these people worship you?"
[34:41] They will answer, "Be You glorified. You are our Lord and Master, not them. Instead, they were worshiping the jinns; most of them were believers therein."
[11:18] Who are more evil than those who fabricate lies about God? They will be presented before their Lord, and the witnesses will say, "These are the ones who lied about their Lord. God's condemnation has befallen the transgressors."
[33:45] O prophet, we have sent you as a witness, a bearer of good news, as well as a warner.
[39:69] Then the earth will shine with the light of its Lord. The record will be proclaimed, and the prophets and the witnesses will be brought forth. Everyone will then be judged equitably, without the least injustice.
When we deliver God's invitation of faith and righteousness through our words and actions, not only we promote and validate His truth but also we are momentarily taking part of the records of others. God beautifully describes how we become responsible for what we have witnessed and appreciated, and how the system of delivering and preserving His Truth is set to work through honest witnesses all the way until the Judgment Day:
[22:78] .... Thus, the messenger shall serve as a witness among you, and you shall serve as witnesses among the people. Therefore, you shall observe the Contact Prayers (Salat) and give the obligatory charity (Zakat), and hold fast to God; He is your Lord, the best Lord and the best Supporter.
[2:143] We thus made you an impartial community, that you may serve as witnesses among the people, and the messenger serves as a witness among you....
[4:41] Thus, when the day (of judgment) comes, we will call upon a witness from each community, and you (the messenger) will serve as a witness among these people.
[16:89] The day will come when we will raise from every community a witness from among them, and bring you as the witness of these people. We have revealed to you this book to provide explanations for everything, and guidance, and mercy, and good news for the submitters.
In conclusion, solid and verifiable evidence is an integral element of divine justice. God sets the highest example of justice and truth by implementing His laws of justice on the Day of Judgment. The witness system is one application. God is in NO need for witnesses but He sets the supreme example only to address the disbelievers' baseless claims by presenting physical proofs. Every single disbeliever will have a witness on that day. Wicked jinns or humans will anticipate their destiny and will offer testimonies against themselves on that day, while the assigned witnesses by God are servants and believers in Him alone. God, the messengers, from the angels or the humans, and assigned truthful believers are going to be witnesses on the Day of Judgment. Witnesses are vital to establish justice on earth and are the keepers of the truth all the way until the Day of Judgment.
[3:53] "Our Lord, we have believed in what You have sent down, and we have followed the messenger; count us among the witnesses."
Peaceful Friday, salaam and God bless.