Seeing a lamb in your dream generally symbolizes your child. If you dream of slaughtering a lamb, it indicates a potential health-related death of your child or another family member's child. This dream serves as a warning, urging you to be more attentive to the well-being of your family members.
From Imam Muhammad Ibn Seerin's Dictionary of Dreams According to Islamic Inner Traditions â entry "Lamb" (page 248).
In a dream, a lamb represents one's son. If one sees himself slaughtering a lamb in a dream, it means that either his son or the son of one of his relatives may shortly die from an illness or an accident. If one is offered a lamb as a gift in a dream, it means that he will beget a noble and a blessed son. If one sees himself eating lamb in a dream, it means that he will earn his money through such a son. If one sees himself herding sheep in a dream, it means that he will profit from a blessed money and acquire honor and fame thereafter. (Also see Sacrifice)
Note: Islamic dream interpretation depends on the dreamer's circumstances and state. This is a general guide drawn directly from the source book.