Does the Prophet’s — may Allah’s prayers and peace be upon him — not specifying the duration of Qasr (shortened prayer), and Ibn Abbas being more knowledgeable of the Sunnah, justify adopting the Hadith of the traveler’s prayer for 19 days in Sahih Al-Bukhari, and not rejecting it despite the difference of opinion among scholars regarding the duration?

Sahih al-Bukhari is the most authentic book after the Quran. Al-Bukhari narrated from Ibn 'Abbas that the Prophet, peace and blessings be upon him, stayed on a journey for nineteen days, shortening the prayer. The opinions regarding the duration of shortening prayer have reached more than twenty sayings, and controversial issues do not rely on a single hadith.

Other sayings have been narrated from Ibn 'Abbas, just as sayings have been narrated from other Companions that contradict what Ibn 'Abbas held.

Scholars have agreed that a traveler who stays to fulfill a need, after which he returns to his hometown, shortens the prayer, even if his stay is prolonged. This is how the hadith of Ibn 'Abbas regarding the Prophet's stay in Makkah was interpreted.

Ibn 'Abbas's statement, "We shorten [prayer] for nineteen [days], and if we exceed that, we perform it in full," was his own ijtihad (independent reasoning), and other Companions disagreed with him. The disagreement among the Companions does not make the saying of one of them an argument against another. The hadith of Ibn 'Abbas was not rejected; rather, scholars differed in understanding it and deriving rulings from it.