A.T. Robertson Commentary Luke 15:18

"I will arise and go to my father, and will say unto him, Father, I have sinned against heaven, and in thy sight:" — Luke 15:18 (ASV)

I will arise and go (αναστας προρευσομα). This determination is the act of the will after he comes to himself and sees his real condition.

I did sin (ημαρτον). That is the hard word to say and he will say it first. The word means to miss the mark. I shot my bolt and I missed my aim (compare the high-handed demand in verse 12).