Did Jesus teach we could become gods since He said "[b]e ye therefore perfect" (Matthew 5:48)?
The immediate context of this Matthew passage tells us in what sense we are to be perfect. We are to be perfect loving our enemies (cf. vss. 43-47). This is what theologians have called a communicable attribute. It is an attribute that God shares with us. Now just because Jesus' disciples must be perfect (mature or lacking nothing), it does not entail they will be gods as God is God (having God's incommunicable attributes: eternally God, omnipotent, omniscient, omnipresent, the originator and sustainer of everything outside Himself, etc.). The Matthew 5:48 passage does not mention anything about becoming "gods," and even if it did, becoming a god is quite different from being God by nature. If the owner of a chimpanzee tells the pet to be as good as its owner is, the owner is not expecting the chimp to miraculously transform into a human being. The owner is simply concerned that her pet act as she would in certain circumstances. Simply sharing a property (viz., perfection) in common is not sufficient for claiming that the two things are of the same nature or species. The angels of God certainly share perfection in common with God, but that doesn't entail that the angels are begotten of God rather than created by God (cf. the distinction between begetting and making in my comments on John 10:34).