Hadithcore
Mishkat al-Masabih, 1250

Abu Umama told of his hearing God’s Messenger say, “If anyone goes to bed in a state of purity and makes mention of God till drowsiness overtakes him, he will not turn round at any time during the night and ask God at that time for some of the good of this world and the next without His giving it to him.” Nawawi mentioned it in <i>Kitab al-adhkar</i> by the transmission of Ibn as-Sunni.

عَنْ أَبِي أُمَامَةَ قَالَ: سَمِعْتُ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ: «مَنْ أَوَى إِلَى فِرَاشِهِ طَاهِرًا وَذَكَرَ اللَّهِ حَتَّى يُدْرِكَهُ النُّعَاسُ لَمْ يَتَقَلَّبْ سَاعَةً مِنَ اللَّيْلِ يَسْأَلُ اللَّهَ فِيهَا خَيْرًا مِنْ خَيْرِ الدُّنْيَا وَالْآخِرَةِ إِلَّا أَعْطَاهُ إِيَّاهُ» . ذَكَرَهُ النَّوَوِيُّ فِي كِتَابِ الْأَذْكَارِ بِرِوَايَةِ ابْنِ السّني

References1 variant
In-Book Reference
Book 4, Hadith 665