The turning back at Sargh

Umar set out from Madinah for Syria, and at a place called Sargh, near the frontier, the commanders of the army came out to meet him. They brought news: there was plague in the land ahead.

Umar stopped and took advice, group by group. The emigrants disagreed among themselves. The Ansar did the same. Then he called the older men of Quraysh, and they were unanimous — turn back, and do not take people into this.

He announced that he would leave in the morning, going back the way he had come.

Abu Ubaydah, who commanded there, put the objection that everyone else was thinking: are you running from what Allah has decreed?

Umar's answer is the line the episode is remembered for. Yes — we are running from the decree of Allah to the decree of Allah. He put it as a question about grazing a camel in a green valley or a barren one: whichever you choose, you are choosing under Allah's decree either way. Being willing to accept an outcome does not oblige you to walk into it.

Then Abd ar-Rahman ibn Awf arrived, having been away, and reported that he had heard the Prophet ﷺ say: if you hear of this sickness in a land, do not go into it; and if it breaks out in a land where you are, do not leave to escape it.

Umar praised Allah and left.

Abu Ubaydah, who had argued the other side, was bound by the second half of that rule. He was already in the land. He stayed with his army, and the plague killed him.