a [came to himself, he said, How many hired servants of my father's have bread enough and to spare, and I perish with hunger]

His condition brought him to his senses and he realized his end if he continued thus. He compared his lot with the servants of his father, making his final decision to go back home and plead for the lowest place in the household

[18] I will arise and go to my father, and will say unto him, Father, I have sinned against heaven, and before thee,

^{a [I have sinned against heaven, and before thee]}

^{This is true repentance—confession of sin, genuine sorrow, and humility because of sin.}

^{Luke 13:3
   [3] I tell you, Nay: but, except ye repent, ye shall all likewise perish.}

 ^a[repent] Greek: metanoeo (GSN-3340), to change one's mind for the better. Not merely to forsake sin, but to change one's attitude toward it and his love for it. Hence, To stop Sining Plain and Simple
it is demanded by God as a condition of forgiveness and grace (Luke 13:3,5; Luke 15:7; Luke 24:47; Acts 2:38; Acts 3:19; Acts 17:30; Matthew 4:17).