How sound is the narration reported from Ali ibn Abi Talib in defining tartil as "beautifying the letters and knowing the pauses"?

The statement attributed to Ali ibn Abi Talib, may Allah be pleased with him, "Tartil is knowing the pauses and perfecting the letters," has not been found with a chain of transmission (isnad) after extensive research. The earliest person to mention it was Abu al-Qasim al-Hudhali in his book "Al-Waqf wal-Ibtida'" without an isnad. He was then followed by Ibn al-Jazari in his books, such as "Al-Tamhid fi al-Tajwid" and "Al-Nashr fi al-Qira'at al-Ashr," as well as other authors, none of whom provided an isnad for it. Therefore, scientific verification necessitates hesitation in accepting and using it as evidence until its origin is found.