tn The construction has: “[The] lamb … will be to you.” This may be interpreted as a possessive use of the lamed, meaning, “[the] lamb … you have” (your lamb) for the Passover. In the context instructing the people to take an animal for this festival, the idea is that the one they select, their animal, must meet these qualifications.
tn Because a choice is being given in this last clause, the imperfect tense nuance of permission should be used. They must have a perfect animal, but it may be a sheep or a goat. The verb’s object “it” is supplied from the context.