When Jesus saw that a crowd came running together, he rebuked the unclean spirit, saying to it, ‘You spirit that keep this boy from speaking and hearing, I command you, come out of him, and never enter him again!’ After crying out and convulsing him terribly, it came out, and the boy was like a corpse, so that most of them said, ‘He is dead.’ But Jesus took him by the hand and lifted him up, and he was able to stand. When he had entered the house, his disciples asked him privately, ‘Why could we not cast it out?’ He said to them, ‘This kind can come out only through prayer.’ (Mark 9: 25-29)

Both Matthew and Luke include this event in their gospels. Matthew's closing is similar in theme, but different in a seemingly important detail.

According to Mark the healing required prayer. Some ancient versions of Mark include fasting. In Matthew the key is trust (Matthew 17:20).

This is the same Greek word that was translated as believe when the father shouted, "I believe, help my unbelief." It is the feminine noun pistis.

It is derived from a verb meaning to persuade. To have faith is to be persuaded. To believe is to be convinced. Convinced of what?

The Hebrew most often compared to pistis is aman. As is typical, the Hebrew is less abstract and more earthy than the Greek.

There are noun forms, but aman is a verb. It means to support, confirm, have faith. It means to be firm, reliable, and verified.

It also means to act as a foster-father, foster-mother, or a nurse. To believe is to be convinced that God nourishes, supports, and cares. To have trust is to be sure that God is trust-worthy.