JST Matt 9:18-21 provides an explicit affirmation of the personal pre-existence of Jesus. The 1867 Inspired Version (an RLDS publication) renders the passage as follows:
18 Then said the Pharisees unto
him, Why will ye not receive us with our baptism, seeing we keep the whole law?
19 But Jesus said unto them, Ye keep not the
law. If ye had kept the law, ye would have received me, for I am he who gave
the law.
20 I receive not you with your baptism,
because it profiteth you nothing.
21 For when that which is new is come, the old
is ready to be away.
The following is an image of the handwritten text of the JST (NT
1, p. 22):