Albert Barnes Commentary 1 Samuel 19:13

"And Michal took the teraphim, and laid it in the bed, and put a pillow of goats` [hair] at the head thereof, and covered it with the clothes." — 1 Samuel 19:13 (ASV)

An image - “Teraphim” was an image, or a bust in human form and as large as life, of a kind of household god to whose worship the Israelites, and especially the women, were very devoted.

A pillow - This was probably a quilt or blanket of goats’ hair, commonly used as a bed covering. It is not clear whether Michal drew it over the head of the teraphim, as if for warmth, and so covered it, or whether she arranged it around the head to look like hair.