What does Matthew 13:6 mean?

Jesus is teaching a large crowd through a parable about a sower planting a field of grain (Matthew 13:1–3). The sower scatters seed all over the field as he walks back and forth across it. The parable describes what happens to the various seeds as they land in different spots in the field (Matthew 13:4–5).

The prior verse mentioned seed falling onto rocky places covered by a thin layer of dirt. Those seeds quickly germinate and spring up. There's just enough soil there for them to sprout, but not enough to develop any real root system. As soon as the hot sun comes up, they die. Without roots in deep soil, there's no support to endure stress. Such plants will not survive.

Jesus later explains this parable to His disciples (Matthew 13:20–21). The seeds represent teaching about the kingdom of heaven to the people of Israel. The hope is that as many people as possible will repent, believe in Jesus as the Messiah, and be prepared to enter the kingdom. Seed sprouting from rocky soil is like the people who hear the message of the kingdom and quickly receive it, despite not having any "root" in themselves. Their acceptance is superficial, like the thin layer of dirt on top of a rock. When hard times or persecution come, they quickly fall away from their faith.