Assalamu alaykum shaykh Please clarify whether when praying should the duration of both prostration and bowing be made shorter in the the third and fourth rakah of a four rakah prayer when compared to it's first two rakahs.

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His Slave and Messenger.

It is from the Sunnah for the imam to lengthen the first two rak‘ahs of a four-rak‘ah prayer and to shorten the last two.

In the two authentic collections, it is reported from Sa‘d ibn Abi Waqqas that he said: “I used to lead them in the afternoon prayer according to the prayer of the Messenger of Allah ﷺ, and I would not fall short in it. I would lengthen the first two rak‘ahs and shorten the last two.” ʿUmar, may Allah be pleased with him, said: “That is what I expected of you.”

Ibn Rajab stated in Fath al-Bari: “The afternoon prayer refers to Dhuhr and ʿAsr.” [End quote.]

In the hadith of Abu Hurayrah describing the Prophet’s prayer, it is mentioned that: “He ﷺ used to lengthen the first two rak‘ahs of Dhuhr and shorten the last two, and he would shorten the ʿAsr prayer.” [An-Nasa’i and others.]

It appears that this shortening includes the bowing (rukuʿ) and prostration (sujud) as well. It was from the guidance of the Prophet ﷺ that when he lengthened the standing, he would lengthen the bowing and prostration; and when he shortened the standing, he would shorten the bowing and prostration. Supporting this is the narration from Abu al-ʿAliyah who said: “Someone who heard the Prophet ﷺ narrated to me that he said: ' Give each surah its due share of bowing and prostration.'” [Reported by Ahmad, and authenticated by al-Albani in Sifat al-Salah.]

Therefore, it is prescribed to shorten the bowing and prostration in the last two rak‘ahs of a four-rak‘ah prayer in comparison to the first two.

Allah Knows best.