What does Judges 4:20 mean?
Sisera has run, on foot, quite some distance to arrive at the encampment of a man named Heber (Judges 4:11, 15–17). Sisera expected to find shelter, since Heber shared a peace treaty with Jabin, king of Hazor and leader of the Canaanites who were oppressing Israel (Judges 4:1–3).Heber does not appear in the story, however. Instead, Heber's wife Jael sees the feared commander of the Canaanite army approaching. She goes out to meet him. She convinces him to hide in a tent, anticipating the inevitable soldiers who will come from Israel's army. She covers him with a rug, likely a thick sheepskin or goatskin, and obliges his request for a drink by giving him milk (Judges 4:18–19). This act implies that she intends to extend full middle eastern hospitality—protecting a guest, affirmed as such when they are given food.
Perhaps Sisera recognizes that fatigue from his escape is catching up with him. He knows he will sleep soon. Before he does, he gives specific instructions to Jael. He tells her to stand guard and lie if anyone asks if someone is inside. Satisfied that he is somewhat safe with Jael's protection, Sisera soon falls asleep inside the tent. As the next verse shows, he won't stand up again (Judges 4:21).