Hadith: O people, seek repentance from Allah and seek His forgiveness. Verily, I seek repentance one hundred times a day

عن الأغر بن يسار المزني رضي الله عنه قال: قال رسول الله صلى الله عليه وسلم : «يا أيُّهَا النَّاسُ، تُوبُوا إلى اللهِ واسْتَغْفِرُوهُ، فَإنِّي أَتُوبُ في اليَّومِ مائةَ مَرَّةٍ».
[صحيح] - [رواه مسلم]

Al-Agharr ibn Yasār al-Muzani (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "O people, seek repentance from Allah and seek His forgiveness. Verily, I seek repentance one hundred times a day."
Sahih/Authentic. - [Muslim]

Explanation

The Prophet (may Allah's peace and blessings be upon him), whose past and future sins had been forgiven by Allah, commanded people to repent and seek Allah's forgiveness and stated that he would seek Allah's forgiveness and repent to Him a hundred times every day, thereby urging people to do the same. The Prophet's pursuit of forgiveness was not necessarily for sins that he had committed, but it was part of his complete servitude to Allah, deep attachment to His remembrance, and the feeling of the tremendous duty towards Him and the shortcoming of His servants no matter how much they show gratitude. His act does also serve the purpose of prescribing the religious deeds for the Ummah.