Mis‘ar bin Kidaam (rahimahullah) narrates the following:

I once went to Imaam Abu Hanifah (rahimahullah) in his Musjid and saw that he was performing the Fajr Salaah. After completing Salaah, he commenced teaching his students, and he continued to teach them until the time for Zuhr Salaah set in. After performing the Zuhr Salaah, he continued to teach the students until the Asr Salaah, and thereafter continued until it was close to the time of Maghrib. Similarly, after performing the Maghrib Salaah, he continued to teach the students until the Esha Salaah.

Seeing the extent to which Imaam Abu Hanifah (rahimahullah) was engaged in teaching the knowledge of Deen, I wondered, within my heart, when it was that he engaged in nafl ‘ibaadah. With this thought in mind, I decided to observe him and thus remained behind him. Once the people had left after Esha, he entered the Musjid. He had applied a perfume of exquisite fragrance that is generally used by a person at the time of marriage. He then stood in Salaah and continued to perform Salaah until the time of Fajr. On completing his Tahajjud Salaah, he proceeded to his home, changed his clothing, and returned to the Musjid where he performed the Fajr Salaah.