13. I--whatever others count as to themselves. He who counts himself perfect, must deceive himself by calling sin infirmity (1Jo 1:8); at the same time, each must aim at perfection, to be a Christian at all (Mt 5:48).
      forgetting those things . . . behind--Looking back is sure to end in going back (Lu 9:62): So Lot's wife (Lu 17:32). If in stemming a current we cease pulling the oar against it, we are carried back. God's word to us is as it was to Israel, "Speak unto the children of Israel that they go forward" (Ex 14:15). The Bible is our landmark to show us whether we are progressing or retrograding.
      reaching forth--with hand and foot, like a runner in a race, and the body bent forward. The Christian is always humbled by the contrast between what he is and what he desires to be. The eye reaches before and draws on the hand, the hand reaches before and draws on the foot [BENGEL].
      unto--towards (Heb 6:1).

JFB.