True meaning of istighfār in Islam
Nahj al-Balāgha|Volume 1|Book 3|Chapter 417
وَالرَّابِعُ: أَنْ تَعْمِدَ إِلَى كُلِّ فَرِيضَةٍ عَلَيْكَ ضَيَّعْتَهَا فَتُؤَدِّيَ حَقَّهَا.
the fourth is to fulfil every obligation which you ignored (in the past) so that you may now do justice with it;