Abu Amr al-Shaybani narrates from Sayyiduna Zayd bin Arqam (may Allah be pleased with him); he said: In the time of the Messenger of Allah (peace and blessings be upon him) we used to talk during the prayer; one of us would speak privately with his companion about something he needed, until this verse was revealed: "Guard the prayers, especially the middle prayer, and stand before Allah in devout obedience" [al-Baqarah: 238], and we were ordered at that time to keep silent.
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 5044