The obligation regarding one who gave false testimony while ignorant of its prohibition

Question:
May Allah reward you. This is a questioner from al-Qassim who says: Honorable Shaykh, when I was in elementary school and ten years old, a dispute arose between my cousin and another person. My cousin asked me to testify, so I testified with him, even though I did not know the reason for the dispute, and I was not present. I was ignorant of false testimony. Am I sinful? Is this testimony considered false testimony? What should I do to clear my conscience?

Answer:
There is no doubt that testimony given without knowledge is false testimony, unless you do not know what you are testifying to except from those who testify to the truth and know it. Therefore, testimony must be based on knowledge of the matter testified to. If you testified while not knowing, merely intending to help the person in whose favor you testified, then this is false testimony and a lie, and it is a major sin among the major sins. So you must repent to Allah the Exalted and Majestic. If this testimony led to a judicial ruling, you must inform the judge of this reality that contradicts the truth, and your conscience will not be cleared except by doing so, or by seeking forgiveness from the person against whom you testified. If he permits it and forgives you, we hope that you will not be sinful. As for remaining silent and leaving the wronged person to continue in his state of being wronged, you would be sinful for that. Yes.