The following is a very simple and clear analysis of the difference between following a prophet and following God:
1 Kings 13:8-24 & 1 Kings 17:8-24
The Man of God and the Prophet
8 And the man of God said unto the king, If thou wilt give me half thine house, I will not go in with thee, neither will I eat bread nor drink water in this place:
9 For so was it charged me by the word of the Lord, saying, Eat no bread, nor drink water, nor turn again by the same way that thou camest.
He knew from the start what God commanded him.
10 So he went another way, and returned not by the way that he came to Beth-el.
11 ¶Now there dwelt an old prophet in Beth-el; and his sons came and told him all the works that the man of God had done that day in Beth-el: the words which he had spoken unto the king, them they told also to their father.
12 And their father said unto them, What way went he? For his sons had seen what way the man of God went, which came from Judah.
13 And he said unto his sons, Saddle me the ass. So they saddled him the ass: and he rode thereon,
14 And went after the man of God, and found him sitting under an oak: and he said unto him, Art thou the man of God that camest from Judah? And he said, I am.
15 Then he said unto him, Come home with me, and eat bread.
16 And he said, I may not return with thee, nor go in with thee: neither will I eat bread nor drink water with thee in this place:
17 For it was said to me by the word of the Lord, Thou shalt eat no bread nor drink water there, nor turn again to go by the way that thou camest.
18 He said unto him, I am a prophet also as thou art; and an angel spake unto me by the word of the Lord, saying, Bring him back with thee into thine house, that he may eat bread and drink water. But he lied unto him.
19 So he went back with him, and did eat bread in his house, and drank water.
He took no thought to what was asked. He trusted the prophet, yet knew what God initially asked of him.
20 ¶And it came to pass, as they sat at the table, that the word of the Lord came unto the prophet that brought him back:
21 And he cried unto the man of God that came from Judah, saying, Thus saith the Lord, Forasmuch as thou hast disobeyed the mouth of the Lord, and hast not kept the commandment which the Lord thy God commanded thee,
22 But camest back, and hast eaten bread and drunk water in the place, of the which the Lord did say to thee, Eat no bread, and drink no water; thy carcase shall not come unto the sepulchre of thy fathers.
For going against what God asked of him, he became cursed.
23 ¶And it came to pass, after he had eaten bread, and after he had drunk, that he saddled for him the ass, to wit, for the prophet whom he had brought back.
24 And when he was gone, a lion met him by the way, and slew him: and his carcase was cast in the way, and the ass stood by it, the lion also stood by the carcase. (Old Testament, 1 Kings, 1 Kings 13)
That is the fruit of following man.
Elijah and the Widow
8 ¶And the word of the Lord came unto him, saying,
9 Arise, get thee to Zarephath, which belongeth to Zidon, and dwell there: behold, I have commanded a widow woman there to sustain thee.
The widow also was initially commanded by the Lord.
10 So he arose and went to Zarephath. And when he came to the gate of the city, behold, the widow woman was there gathering of sticks: and he called to her, and said, Fetch me, I pray thee, a little water in a vessel, that I may drink.
11 And as she was going to fetch it, he called to her, and said, Bring me, I pray thee, a morsel of bread in thine hand.
12 And she said, As the Lord thy God liveth, I have not a cake, but an handful of meal in a barrel, and a little oil in a cruse: and, behold, I am gathering two sticks, that I may go in and dress it for me and my son, that we may eat it, and die.
She did what the Lord initially asked of her; she knew of the great sacrifice it would cost.
13 And Elijah said unto her, Fear not; go and do as thou hast said: but make me thereof a little cake first, and bring it unto me, and after make for thee and for thy son.
14 For thus saith the Lord God of Israel, The barrel of meal shall not waste, neither shall the cruse of oil fail, until the day that the Lord sendeth rain upon the earth.
15 And she went and did according to the saying of Elijah: and she, and he, and her house, did eat many days.
16 And the barrel of meal wasted not, neither did the cruse of oil fail, according to the word of the Lord, which he spake by Elijah.
Her faith brought much fruit; but even after her faith, she endured a hard trial:
17 ¶And it came to pass after these things, that the son of the woman, the mistress of the house, fell sick; and his sickness was so sore, that there was no breath left in him.
18 And she said unto Elijah, What have I to do with thee, O thou man of God? art thou come unto me to call my sin to remembrance, and to slay my son?
19 And he said unto her, Give me thy son. And he took him out of her bosom, and carried him up into a loft, where he abode, and laid him upon his own bed.
20 And he cried unto the Lord, and said, O Lord my God, hast thou also brought evil upon the widow with whom I sojourn, by slaying her son?
21 And he stretched himself upon the child three times, and cried unto the Lord, and said, O Lord my God, I pray thee, let this child’s soul come into him again.
22 And the Lord heard the voice of Elijah; and the soul of the child came into him again, and he revived.
The fruit of a true prophet:
23 And Elijah took the child, and brought him down out of the chamber into the house, and delivered him unto his mother: and Elijah said, See, thy son liveth.
24 ¶And the woman said to Elijah, Now by this I know that thou art a man of God, and that the word of the Lord in thy mouth is truth. (Old Testament, 1 Kings, 1 Kings 17)