question #3 Sahih al-Bukhari 758, Book 10, Hadith 152 : What is the significance of prolonging the first two rak’ahs and shortening the last two in prayer?

Sa`d said, “I used to pray with them a prayer similar to that of Allah’s Messenger (ﷺ) (the prayer of Zuhr and
`Asr) reducing nothing from them. I used to prolong the first two rak`at and shorten the last two
rak`at.” `Umar said to Sa`d “This was what we thought about you.”