Elijah was a prophet of God at a time when the king of Israel, Ahab, married Jezebel, a worshipper of Baal. God was angry with Ahab. Elijah said so. The Lord told him "Go hide by the Wadi Cherith. It has plenty of water, and I'll see you get food." Elijah did what he was told, and things worked out for a while. Then the wadi ran dry (16:29-17:7).
The Lord told Elijah where to go for food.
I'm thinking about how unlikely the choice might have seemed to Elijah. The place was at the center of Baal worship. The person he was supposed to get help from was a woman. He, a stranger, was supposed to approach a woman. Moreover, she was a widow; that is, she wouldn't be expected to have much in the way of financial resources.
But, the Lord had included the assurance, "I have have commanded her to feed you."
Elijah trusted the Lord enough to comply with the instruction.
When he got to the widow's place and asked her for some food, she told him, "As sure as the Lord your God lives, I have only enough for me and my son to have one small meal and then we'll die."
Apparently although she lives in Sidon, she knows about the God that Elijah worships--and obeys.
Elijah responds to her, "Do not be afraid. Go ahead and fix the meal for you and your son, but, first, make me a little cake. The Lord God of Israel will provide you with all the food you need for as long as you need."
She did. And the Lord did.
She trusted God's word that came to her through a prophet, a foreigner.