Believe in the LORD your God, so shall ye be established; believe His prophets, so shall ye prosper (2 Chronicles 20:20b).
There is a supernatural blessing that people receive when they sow into a prophet's ministry. From Biblical days until today, the Lord has always designed it that the prophet would be sustained by the people's gifts.
Some scriptures that speak on giving to the prophet include:
I Samuel 6:6-8
He said to him, "Behold now, there is a man of God in this city, and the man is held in honor; all that he says surely comes true. Now let us go there, perhaps he can tell us about our journey on which we have set out." Then Saul said to his servant, "But behold, if we go, what shall we bring the man? For the bread is gone from our sack and there is no present to bring to the man of God. What do we have?" The servant answered Saul again and said, "Behold, I have in my hand a fourth of a shekel of silver; I will give it to the man of God and he will tell us our way."…
2 Kings 8:8-10
The king said to Hazael, "Take a gift in your hand and go to meet the man of God, and inquire of the LORD by him, saying, 'Will I recover from this sickness?'" 9So Hazael went to meet him and took a gift in his hand, even every kind of good thing of Damascus, forty camels' loads; and he came and stood before him and said, "Your son Ben-hadad king of Aram has sent me to you, saying, 'Will I recover from this sickness?'" Then Elisha said to him, "Go, say to him, 'You will surely recover,'
I Kings 14:1-4
At that time Abijah son of Jeroboam became ill, and Jeroboam said to his wife, “Go, disguise yourself, so you won’t be recognized as the wife of Jeroboam. Then go to Shiloh. Ahijah the prophet is there—the one who told me I would be king over this people. Take ten loaves of bread with you, some cakes and a jar of honey, and go to him. He will tell you what will happen to the boy.” So Jeroboam’s wife did what he said and went to Ahijah’s house in Shiloh.
2 Kings 4:42
And there came a man from Baal-shalisha, and brought the man of God bread of the firstfruits, twenty loaves of barley, and full ears of corn in the husk thereof. And he said, "Give unto the people, that they may eat."