There are several things to note regarding these few words in Luke 23:34, but I will mention just 3. Firstly, forgiveness is only given after a person repents of their wrong doing towards you.If they do not repent, you pray for them,ensuring no ill-feeling,grudges,animosity etc,but you do not forgive. Secondly, it appeared that the enemies of Christ were beyond saving; the mock trial, the clamoring voices "Crucify Him", a death of intense suffering & shame (they couldn't have gone any further,could they?). Yet, our Lord, on the cross, continues to pray for them!! This is a great example to us; when often it appears that our attempts at converting friends and family look doomed to failure, and we almost reach a point of saying "They're not listening, let them get on with it", that we need to continue in prayer. I'm reminded of Elijah (1 Kings 19) after slaying 450 false prophets, was still hounded by Jezebel, and hid himself in a cave; believeng he was the only Christian alive. God rebuked him: "What are you doing here?" (in other words, get on with the job I've commissioned you to do). We are not to give up and feel sorry for ourselves. Thirdly, why did Christ say "Father, forgive them" when He had forgiven people Himself throughout His ministry? This was because at that particular moment He was the sacrificial lamb, therefore unable to excercise His divine authority as God. I pray these few words will help you in your understanding of scripture & a greater knowledge of God.