Musannaf Ibn Abi Shaybah

Hazrat Ali (may Allah be pleased with him) and Ibrahim say that prompting the Imam is speech.

Hazrat Ibn Masood, regarding prompting the Imam, says that it is speech. Ibrahim says that in my view, prompting the Imam and calling your maidservant "Ya Kabirah" are equal.

Hazrat Salm bin Atiyyah says that a man prompted Imam Shurayh during prayer; when he finished the prayer, he said, "Repeat your prayer."

Hazrat Humaid bin Abdur Rahman considered it undesirable that a prompter be given to the reciter.

Hazrat Aamir says that whoever prompted the Imam has spoken.

Hazrat Ali (may Allah be pleased with him) considered it undesirable to prompt the imam during prayer.