Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said, in the narration that has reached us from him concerning the prohibition of speaking in prayer: "So when we returned from the land of Abyssinia."
His return from Abyssinia took place before the emigration of the Prophet (peace and blessings be upon him) to Madinah; then he emigrated to Madinah and took part in the Battle of Badr with the Prophet (peace and blessings be upon him). So this incident of the salam took place before the emigration.
Abdullah bin Mas'ud (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) sent us to the Negus (al-Najashi), and we were 80 men; with us was Ja'far bin Abi Talib (may Allah be pleased with him) as well. He mentioned the complete hadith about their entering the court of the Negus, and at its end it says that Ibn Mas'ud (may Allah be pleased with him) hastened to come back, and he also took part in Badr.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3919