Hadrat Imām Abū Yūsuf rahimahullāh relates an astonishing incident with regard to Imām A‛zam Abū Hanīfah rahimahullāh. You all are probably aware that Imām Sāhib rahimahullāh performed Fajr salāh with the wudū’ of ‛Eshā salāh for forty years. This is well-known. But what is the background to it?
Imām Abū Yūsuf rahimahullāh relates that Imām A‛zam rahimahullāh was going somewhere when, along the way, two people were conversing with each other. When they saw Imām A‛zam rahimahullāh, one said to the other: “This is Abū Hanīfah who performs the fajr salāh with the wudū’ of ‛Eshā salāh every day.”
This was not really true because it was not Imām A‛zam’s rahimahullāh practice to perform the Fajr salāh with the wudū’ of ‛Eshā salāh. However,Allāh ta‛ālā cast this idea in the person’s heart because He probably wanted it to become Imām A‛zam’s rahimahullāh daily practice. When Imām A‛zam rahimahullāh overheard their conversation, he felt very ashamed and thought to himself: “These servants of Allāh ta‛ālā are having such good thoughts about me whereas I am not as they say. I should definitely try to be like that.”
Imām Abū Hanīfah rahimahullāh said: “Glory to Allāh! O Abū Yūsuf! Do you see how Allāh ta‛ālā has caused people to speak about me?! How bad it will be if Allāh ta‛ālā sees me practicing contrary to this. By Allāh! I cannot allow people to attribute
something to me which I do not do.” He made a firm resolution there and then.
Ever since that day until his death, he spent the entire night in worship, performing the Fajr salāh with the wudū’ of ‛Eshā salāh. This continued for about forty continuous years.
Source: Who Is An Aalim E Rabbani