If TREK TO SINAI ends up being about the same length as ESCAPE FROM GOSHEN, I'm about halfway through the first draft. But Leah and Jacob aren't halfway through the trek! They've made it to Rephidim, the high plain surrounding Mt. Sinai (which the Israelites call the Mountain of God). Rephidim is the site of a famous battle with the Amalekites, which the Israelites could only win as long as Moses was lifting both of his hands. After several hours, he needed helpers to keep his arms up. That's the subject of the painting you see above.
In TREK TO SINAI, there's nothing magical about Moses' hands going up. It's a signal to the Israelite warriors. According to this Wikipedia article, the Amalekites seem to have been "known for being unusually tall." I started wondering how the exhausted Israelites, who had been walking along desert riverbeds and climbing into the high country for more than six weeks since they had crossed the Red Sea, could have survived a surprise attack by well-armed nomads who were taller than they were.
Then I realized that they probably wouldn't have been surprised at all. Lots of people would have heard about how the Egyptians gave the Israelites gold and silver when they left Goshen after the final plague; Moses and the other leaders would have been expecting an ambush. Moses also knew the area well - this was where he had lived for years as a shepherd - and he knew that the Amalekites would only have a few places to mount an offensive.
So Moses, his sister Miriam, and Joshua - their top strategist - devised a plan that would give the shorter Israelite fighters an advantage over their taller adversaries. The Israelites would wear rawhide vests under their cloaks. At a signal from Moses, they would pull out hidden knives, bend down low and attack the Amalekites' legs, cutting the tendons behind their knees. The Amalekites would try to put their spears into the Israelites' backs, but the unseen vests would protect the Israelites - at least somewhat. As long as Moses kept his arms up, the Israelite warriors were supposed to fight in this sneaky, unexpected way.
The Torah (Hebrew Bible) is full of stories about how the youngest and smallest achieves the most - from Israel's youngest son Joseph who went from being sold into slavery by his brothers to becoming the viceroy of Egypt, to King David who killed the giant Goliath with a slingshot when he was just a teenager. This idea follows in that same tradition. But I'm pretty proud of it because it's all mine - I've never read anything like it anywhere.