What does Mark 12:34 mean?

One of the scribes, an expert in the Mosaic law, has asked Jesus to identify the primary commandment. Jesus responds that if we know God, love God, and love others, we will fulfill the whole Law. The scribe responds that this three-fold commandment even trumps the system of offerings and sacrifices God developed to cover the sins of the Israelites and honor Him.

The phrase "kingdom of God" has been interpreted to mean "going to heaven." While heaven is certainly part of the kingdom of God, the phrase encompasses much more. It means any situation where God's glory and authority are on display. In this case, it means that the scribe's acknowledgement of the spirit of the Law and how it supersedes the specifics of the Law has led him very close to an understanding of the truth of God's plan of salvation. By discussing the Law, the scribe has stumbled to within a few steps of Jesus.

It's a provocative statement. This scribe, who identifies with a group of religious leaders who are attempting to have Jesus arrested, stands affirmed by Jesus and is very close to being accepted by Him—the same Jesus who only recently overturned the tables of the merchants who supplied the sacrifice-as-business industry (Mark 11:15–19). Some leaders do understand and believe in Jesus, but they fear the shame of the rejection of the Pharisees and the loss of approval of the people (John 12:42–43). Others believe and follow Jesus in secret (John 19:38).

After the Herodians and Pharisees (Mark 12:13) ask Jesus about taxes, His answer silences them (Luke 20:26). After Jesus answers the Sadducees about the resurrection, they, too, fall quiet (Luke 20:40). Now that Jesus has not only answered but shown encouragement to a scribe, this final group grows still. Once Jesus shows the crowd how the Messiah will rule over David, no one will dare ask Him anything more (Matthew 22:46).