قَائِلٌ, بَائِعٌ and خَائِفٌ are active participles. Although each has a visible hamzah, their second radicals are originally wāw or yāʾ.
Word / formMeaning / explanation
قَائِلٌroot ق و ل; one who says.
بَائِعٌroot ب ي ع; one who sells.
خَائِفٌroot خ و ف; one who fears.
Do not reclassify these as hamzah-middle roots just because the surface active participle contains hamzah. Morphological classification follows the original root.