(Ibid.) "then he and his neighbor next to his house shall take it": R. Akiva says: Whence is it derived that if one wishes to make his Pesach for himself he may do so? From "then he and his neighbor shall take." R. Yishmael says: Whence is it derived that if one wishes to appoint others for his lamb he may do so? From "then he and his neighbor, etc." ("neighbor":)
What If a Household Was Too Small to Eat an Entire Passover Lamb
Mekhilta Tractate Pischa 3:14