In Mat.3:2 John urges people to convert. Was it from the Law to Jesus as the Messiah, seeing that the message of salvation was not yet “available”? And when Jesus sends out the disciples in Matt.10 it is with the same message, but here too, the full message, to which people are converting today, was not yet fulfilled. When Jesus in Mat.28 sent them out to evangelise, the way of (to) salvation was clear. Could you please tell me what the message of the first two instructions was?
The message of Matthew 3:2 and 10:7 is that the Kingdom of Heaven is at hand. This means that Jesus had come to offer Israel their long awaited kingdom.
In Matthew 3:2 John added the command to repent. In doing so John was telling them they need to change their minds from relying on keeping the law for their salvation to relying on the Lamb of God who had come to die for their sins.
In Matthew 28:16-20 Jesus was sending the disciples and us into all the world to teach the gospel message.
The difference in the three statements is that the first two were meant for Israel, and the third was meant for the whole world.