Bulugh al-Maram 142
In another version by Al-Bukhari, he (ﷺ) said:
"And perform ablution for every Salat (prayer)". Abu Dawud and others transmitted a similar narration.
وَفِي رِوَايَةٍ لِلْبُخَارِيِّ: { وَتَوَضَّئِي لِكُلِّ صَلَاةٍ }  وَهِيَ لِأَبِي دَاوُدَ وَغَيْرِهِ مِنْ وَجْهٍ آخَرَ.‏