Here are several Questions and Answers from Fisher's Catechism:
Q. 3. What should we rest from on the Sabbath?
A. Even from such worldly employments and recreations as are lawful on other days; or, which is the same thing, from all servile work, Neh. 13:15-23.
Q. 4. What is it that makes a work servile?
A. If it is done for our worldly gain, profit, and livelihood; or if, by prudent management, it might have been done the week before; or, if it be of such a kind as may be delayed till after the Sabbath, Ex. 34:21 — “Six days thou shalt work, but on the seventh thou shalt rest: in shearing* time, and in harvest thou shalt rest.”
Exodus 34:21 (ESV) (for clarity)
"Six days you shall work, but on the seventh day you shall rest. In *plowing time and in harvest you shall rest.
Q. 5. Why does God enjoin rest on the Sabbath so peremptorily and particularly, in the time of ploughing and harvest?
A. Because in these seasons men are most keenly set upon their labour; and may be in the greatest hazard of grudging the time of the Sabbath for rest.
Q. 6. If the weather is unseasonable through the week, do not reaping and ingathering, in that case become works of necessity on the Sabbath?
A. By no means; because any unseasonableness of the weather that may happen, being common and general, proceeds only from the course of God’s ordinary providence, which we ought not to distrust, in regard of his promise, that, “While the earth remaineth, seed-time and harvest —shall not cease,” Gen. 8:22.
Q. 7. If a field of corn is in hazard of being carried away by the unexpected inundation of a river, is it lawful to endeavour the preservation of them upon the Sabbath?
A. Yes; because the dispensation is extraordinary; the case not common nor general; and the damage likewise in an ordinary way, irrecoverable.
Q. 8. Are Christians, under the New Testament, obliged to as strict an abstinence from worldly labour, as the Jews were under the Old?
A. Yes, surely; for moral duties being of unchangeable obligation, Christians must be bound to as strict a performance of them now, as the Jews were then, Psalm 19:9.