The prayers of the Messenger of Allah ﷺ and the prayers of Abu Bakr were close in length, until Umar lengthened the Fajr prayer.
حدثنا إسماعيل ابن علية عن حميد
كانت صلاة رسول الله ﷺ متقاربة وصلاة أبي بكر حتى مد عمر في صلاة الفجر
Its chain of transmission is sahih, and it is found in Muslim, 1/344, no. 473, in the Book of Prayer, on the moderation in the pillars of prayer.