A.T. Robertson Commentary Matthew 13:36

"Then he left the multitudes, and went into the house: and his disciples came unto him, saying, Explain unto us the parable of the tares of the field." — Matthew 13:36 (ASV)

Explain unto us (διασαφησον ημιν). Also in 18:31. "Make thoroughly clear right now" (aorist tense of urgency). The disciples waited till Jesus left the crowds and got into the house to ask help on this parable. Jesus had opened up the Parable of the Sower and now they pick out this one, passing by the mustard seed and the leaven.