Q: Is it not sinful to do something on Sunday?
A: To do something for the glory of God is not sinful, for the Apostle said: working day and night, lest we burden anyone (1 Thess. 2:9); but to do anything not according to God, with disdain (for Sunday), out of greed or from forms of low love of gain is sin. In general, it is profitable on Sundays, on the Lord’s feasts and the days of commemoration of the Holy Apostles, to put away work and come to church, for the tradition of the Holy Apostles teaches this. (Guidance Toward Spiritual Life, 758)