بُلُوغُ الْمَرَامِ
Bulugh al-Maram 153
The Book of Prayer
وَمِنْ حَدِيثِ أَبِي مُوسَى: { وَالشَّمْسُ مُرْتَفِعَةٌ } [1] .
And Abu Musa (RA) narrated regarding the time of 'Asr prayer: "While the sun is high." [Reported by Muslim in another narration of the former Hadith].
Sunnah.com reference: Book 2, Hadith 3