Mishkat al-Masabih 4 Prayer كتاب الصلاة 391

وَعَنْ أَبِي أُمَامَةَ قَالَ: قِيلَ: يَا رَسُولَ اللَّهِ أَيُّ الدُّعَاءِ أَسْمَعُ؟ قَالَ: «جَوْفُ اللَّيْلِ الآخر ودبر الصَّلَوَات المكتوبات» . رَوَاهُ التِّرْمِذِيّ

Abu Umama said that God’s Messenger was asked which supplication is most readily listened to, and replied, “What is offered in the latter part of the depth of the night and after the prescribed prayers.” Tirmidhi transmitted it.