A.T. Robertson Commentary Luke 13:9

"and if it bear fruit thenceforth, [well]; but if not, thou shalt cut it down." — Luke 13:9 (ASV)

And if it bear fruit thenceforth (κ'αν μεν ποιηση καρπον εις το μελλον). Aposiopesis, sudden breaking off for effect (Robertson, Grammar, p. 1203). See it also in Mr 11:32; Acts 23:9. Trench (Parables) tells a story like this of intercession for the fig tree for one year more which is widely current among the Arabs today who say that it will certainly bear fruit this time.