Ibnu ‘Umar (radhiyallahu ‘anhuma) has reported that Nabi (sallallahu ‘alaihi wasallam) would recite istighfaar seventy times in each majlis (sitting).

(Through this we understand the importance of istighfaar and how necessary it is for us to make istighfaar. Despite Allah Ta‘ala stating in the Quraan Majeed with regards to Nabi (sallallahu ‘alaihi wasallam):

لِّيَغْفِرَ لَكَ اللَّـهُ مَا تَقَدَّمَ مِن ذَنبِكَ وَمَا تَأَخَّرَ

Allah Ta‘ala has forgiven all your past and future shortcomings. (Surah Fath, v2)

and him being sinless, yet Nabi (sallallahu ‘alaihi wasallam) would still make so much of istighfaar in each sitting. Hence, how much more should we endeavour in making istighfaar due to our countless shortcomings.) (Malfoozaat of Faqeehul Ummat, vol. 1, pg. 410)