Complex sentence: The Synod of Lambeth under Archbishop Peekham, in 1281, was content to order priests to explain the truths of faith four times year, but the Provincial Council of Lavour, in 1368, commanded parish priests to give instruction on all Sundays and feast days.
Split into simpler sentences: The Synod of Lambeth under Archbishop Peekham, in 1281, ordered priests to explain these truths of faith four times year. The Provincial Council of Lavour, in 1368, expanded this and commanded parish priests to give instruction on all Sundays and feast days.