الباسط
كلمة (الباسط) في اللغة اسم فاعل من البسط، وهو النشر والمدّ، وهو...
The original witness asks a secondary (branch) witness to remember his testimony and memorize it accurately so that he would relay it on his behalf (before a judge).
"Shahādat al-istir‘ā’" (secondary testimony/testimony to testimony) is when the original witness says to another person (the secondary witness): "Bear witness to my testimony and memorize it." So it is the duty of the secondary witness and anyone else who hears the original witness's testimony to testify based upon that testimony, even if the original witness did not specify others than the secondary witness in doing so. An example: A person has a right usurped by a strong tyrant, and that person fears that his right would be lost with the passage of time, so he secretly asks another person to bear witness that he will continue to claim his right and will not relinquish it to the tyrant.