The proclamation of the kingdom of God
Everyone is called to enter the kingdom. First announced to the children of Israel, this messianic kingdom is intended to accept men of all nations. To enter it, one must first accept Jesus' word:
The word of the Lord is compared to a seed which is sown in a field; those who hear it with faith and are numbered among the little flock of Christ have truly received the kingdom. Then, by its own power, the seed sprouts and grows until the harvest.
Source: Catechism of the Catholic Church (Vatican.va)