The Messenger of Allah ﷺ used to point with his index finger during the prayer.
حدثنا عبد الرحمن بن مهدي عن سفيان عن منصور عن أبي سعيد الخزاعي
ى أن رسول الله ﷺ كان يشير بأصبعه السباحة في الصلاة
No references are available.
Its isnad is sahih. In it appears as, "Mansur from Abu Saeed Khuzai," which is an error. It is actually Saeed bin Abdul-Rahman bin Abza Khuzai. The hadith has already appeared at 12347, and it is found in Muslim and others.