Charles Ellicott Commentary Matthew 9:21

"for she said within herself, If I do but touch his garment, I shall be made whole." — Matthew 9:21 (ASV)

She said within herself—these words indicate a faith that was real but not strong. She believed in His power to heal, as the leper did, but did not trust in His love, and she shrank from the thought, afraid that the Healer might shrink from her. Her faith was not in a will that actively seeks to bless and save, but in a physical outflow of power passing from His body to His garments, and from the garments to the hand that touched them.

Yet, as weak as this faith was, it was accepted, and physical objects were endowed with a "virtue" that was not their own. In the same way, when a similar belief was present later, handkerchiefs and aprons brought from Paul's body became a means of healing (Acts 19:12).