Strejc was born in Autumn 1592, probably in Hranice na Moravě as the fourth son of Jiří Strejc, a writer, translator of religious texts and organizer of Unity of the Brethren in Židlochovice in southern Moravia. Young Strejc first studied in Herborn, later at the gymnasium in Bremen and then teology at the University of Heidelberg. In Heidelberg, in 1620, he became a Czech tutor for the oldest son of Elector Palatine Frederick V (shortly reigning as the Czech king). Later, Strejc studied at the academy in Leiden. In 1632 he joined the exiled community of Unity of the Brethren in Leszno, Poland and in the same year became priest and administrator of Unity's printing-shop. In Leszno he married Kristina Poniatowska, foster-daughter of Commenius famous for ecstatic prophecies. The couple had two sons and three daughters. In 1655, during the Northern War, Leszno was burned down and the community destroyed. Strejc and the remains of the Unity moved to Brzeg (Břeh) in Silesia, the new centre for the exile.