I accompanied the Messenger of Allah ﷺ on eighteen journeys, and I never saw him omit the two units of prayer offered after the sun's decline, before the noon prayer.
حدثنا قتيبة بن سعيد حدثنا الليث عن صفوان بن سليم عن أبي بسرة الغفاري
صحبت رسول الله ﷺ ثمانية عشر سفرا فما رأيته ترك ركعتين إذا زاغت الشمس قبل الظهر
Sourcing, its isnad is hasan. Tirmidhi narrated it in the Book of Prayer, chapter on what has been said about voluntary prayer while traveling, 1/315, and Hakim concurred with him and graded it sahih according to the criteria of the two Shaykhs, hadith no. 550, from Qutayba with the same wording, and he said, "Gharib." Dhahabi agreed.