What is the disagreement between Imam Al-Shafi'i and Imam Abu Hanifa that leads to a difference in performing the Asr prayer?

The imams did not differ on the fundamentals of religion or the branches known by necessity. Rather, they differed on jurisprudential branches where there was no clear, definitive text. This is natural due to the varying capacities of minds in understanding the evidence. An example of a definitive matter is His (Allah's) saying: "Allah instructs you concerning your children: for the male, what is equal to the share of two females" (Quran 4:11). An example of a matter that allows for difference is His saying: "Divorced women remain in waiting for three periods" (Quran 2:228), where scholars differ on the meaning of "periods" (qurū’). Differences occurred even among prophets and companions. Disagreement should not be used as a means for division and fanaticism, for the imams differed in their ijtihad (independent reasoning) based on what they deemed to be true and in conformity with the شرعية (Sharia) evidence.