There is a beautiful old word "fiat." No, I'm not talking about the car! It comes from a Latin word meaning "to make, or to do." In the Latin Vulgate version of the Bible God commanded "Let there be light" (1:3). The Latin says, "fiat lux." So the word came to be used in official commands and royal decrees: "Let it be so what I have said." When an official fiat was given, the king's command became the law of the land. The fiat became fact as soon as the words were spoken. When God declared, "Let there be light" there was no committee established to design what "light" should be. When God said it, it was so!
Now we have these words in Romans 5:1: "Therefore, since we have been declared righteous by faith...." The meaning is this: the moment we put our faith in Jesus as our Savior, at that same instant we are declared "righteous" by God! There is no probationary period--no "wait and see see if we measure up." The contract reads: "we have been declared righteous...." The Greek is all one word, dikaiothentes--an aorist passive participle. It all means something. Aorist means "past tense, continuing results." If I wrote about spilling coffee on my white shirt I'd use the aorist tense, meaning--in effect--"The resulting stain is permanent--and now I use the shirt to change the oil in my car! "Declared" is also in the passive voice. The passive means that I am not the one who acts, or even participates in the action, but I am acted upon. If I was run over by a horse, and I lived to write about it, I'd say "that dumb horse ran over me"--passive voice. I did not run over myself. I was not riding the horse when it ran over me. The horse did it--which has actually happened to me--twice! And then, finally, it is a participle, or, more precisely, a participial phrase--pointing to the Actor, who is--in this case--God.
So--putting it all together--what does this mean? At that moment when I put my trust in Jesus God declared me righteous. I am righteous by fiat of God. I am not on probation. I do not have to prove that I measure up to what God has declared. The same God who--by His word--spoke the worlds into existence, spoke the word and declared me righteous! The results are permanent. I did not do anything to deserve this new state, and I cannot do anything to cancel it. God's fiat made my new standing a fact--forever!