‘On that day Jesus went out of the house, and sat by the sea side.'
Note again the usual vague connecting introduction. While Jesus was possibly in a house in Matthew 12:46-50 it was never made explicit, although if He was He must have been preaching from the door for He was speaking to the crowds. Why then mention the house here? The reason would seem to be in order to stress that what follows immediately afterwards is spoken to those ‘outside' as in Matthew 12:47. This was a message for ‘the crowds', not for the inner group of disciples. The open land at the side of the sea provided plenty of room for the crowds.
‘The house'. This may in fact signify the equivalent of ‘my house', thus being the house of the writer who remembered the scene vividly. If he was a former public servant he would have had a larger house than most which would have been useful for accommodating the growing band of followers.