What is the ruling on a just witness who denies having knowledge of a testimony but later recalls and testifies, claiming forgetfulness?

Primary text

If a just individual denies possessing testimony concerning a matter, but subsequently testifies to it, claiming he had forgotten it, his testimony is accepted, and it is not rejected. This is the position of Al-Thawri, Al-Shafi'i, and Ishaq, and no opposition to this view is known. This is permissible because it is possible that he forgot it, and if he was forgetful, he genuinely possessed no testimony at that moment. Therefore, he is not deemed a liar when his statement is possible. This situation is distinguished from a case where a person says, 'I have no evidence,' and later produces evidence, which is not accepted, because the initial statement is an admission against himself regarding the absence of evidence, and a person is held accountable for his admission. Stating 'I have no testimony' is not an admission because the testimony is not his right; rather, it is a right owed by him, making his statement a denial. When he later acknowledges it, it becomes an admission after denial, which is heard. The forgetful person genuinely has no testimony with him when denying, so his denial is truthful, and when he remembers, it becomes present with him, reconciling the two statements. This is analogous to someone denying having testimony before being summoned to testify, and then testifying once it is present with him.