Old World Context: This saying takes a common task and alters the context from the mundane to the spiritual. The cultural setting requires houses with doors. We go looking for someone, and we come to where that person should be, and we knock as an indication that we are seeking someone inside. The knock is taken as a signal, and one in the interior opens the door. Obviously, this custom continues, and is made more obvious by the addition of the doorbell that may even more loudly and obviously announce the fact that someone we cannot see is seeking someone inside the house.
In the social setting of the saying, the expectation is that a door that is knocked will be answered. We seek a friend in their home, announce our intent to see them by knocking, and the door that keeps us out is opened and we are invited in. This is social custom and common occurrence.
This common event becomes symbolic when it is applied to the vertical relationship with God rather than the common horizontal relationship with other people. The point of the example is to show that God stands in relationship to us as would any friend or relative. While God might be in his “house,” he is nevertheless willing to receive us if only we do that which we would do to seek any friend or relative. We come to where God is, and we knock on the door. The promise is that God will open. He will not be inhospitable and ignore the knocking.
Of course we approach God in prayer, and our prayers are the petition of knocking on God’s symbolic door. This is the promise that they will be received, and that God will invite us in. Remember that when Jesus taught the people to pray they were to address God as Father, and therefore as kin. Of course one’s kin will open the door. It is only to be expected.
Book of Mormon Context: As with the example of the pearls and swine, the meaning of this saying would have had to be altered to fit the appropriate cultural contexts. We do not know the customary mode of the ancient Nephites for announcing themselves to those in the interior of a house, but it is rather certain that they did not knock, as there were no doors. Doors were typically fabric hung on the doorway, not wooden obstructions. Thus the knocking on the door image could not have been relevant, though obviously the imagery of God as kin graciously receiving us would have been quite appropriate.
Textual: There are no changes from the Matthean text.