Imam Ali (AS) wrote in a letter to Muhammad b. Abu Bakr, ‘Observe the timing of the prayer and perform it at its prescribed time, neither hastening to pray it earlier in order to be free of it, nor delaying it because of some work.
الإمامُ عليٌّ (عَلَيهِ الّسَلامُ) ـ مِن كتابِهِ لمحمّدِ بنِ أبي بكرٍ ـ: اِرتَقِبْ وَقتَ الصَّلاةِ فَصَلِّها لِوَقتِها، ولا تَعَجَّلْ بها قَبلَهُ لِفَرَاغٍ، ولا تُؤخِّرْها عَنهُ لِشُغلٍ.
Similar narrations
Nahj al-Balāgha #1305Say prayers at the appointed time. Do not say it earlier for the sake of (available) leisure nor delay it on account of pre-occupation....