These two verses have a very primary sound. The difficulty of them is much against their invention by Luke or anyone in his time. But if Luke derived them from any written source, they are exactly such sayings as would have found a place in his recension of Q.
This saying was evidently spoken in Jerusalem, but Luke has placed it during the journey thither. We may perhaps detect here the beginnings of a Jerusalem tradition.
Like the preceding, the parable is given as part of the conversation on the Samaritan journey. But it seems to be Luke's version of the story told by Mark of the cursing of the fig tree; and this latter Mark places in Jerusalem. This may be taken as another hint of the origin of this section in a Jerusalem tradition.
Mr. Streeter[114] remarks of this section that it is so "un-Lucan in its rough vigor that it is certainly original"; in other words, that it certainly stood in Luke's source. This source Mr. Streeter maintains is Q, not only for this brief section, but for the solid block of Lk ix, 51-xiii, 59 (with the possible exception of the two parables of the Good Samaritan, the Rich Fool, and perhaps the story of Martha). The passage, xiii, 1-17, he suggests may have been interpolated into Q before Q came to Luke.
The primary character of the section now under consideration cannot be doubted. The fact that Luke has apparently left his Q material by itself, instead of mingling it with his Marcan and other matter, would argue for Mr. Streeter's position. Yet Luke has not altogether followed this general rule of his; and he has made some very notable transpositions of Marcan material. This saying, also, is not quite like most of the sayings that are by common agreement to be ascribed to Q. It is neither a general rule of conduct, like the sayings in the Sermon on the Mount, nor has it to do with the kingdom of God, like the brief parables of Q. If Luke inserted it from another source, his reason for inserting it in just this place may have been the fact of its closing with the word "Jerusalem." Yet the lament over Jerusalem which immediately follows is evidently wrongly placed by Luke, in the midst of his Perean journey. We are inclined to assign these verses, tho with some uncertainty, to a special source. The words were apparently spoken neither on the Perean journey (assuming such a journey to have taken place) nor at its close in Jerusalem, but in Galilee.