The place you are nearest to Him
The Prophet ﷺ named the exact posture in which a servant is closest to his Lord.
أَقْرَبُ مَا يَكُونُ الْعَبْدُ مِنْ رَبِّهِ وَهُوَ سَاجِدٌ فَأَكْثِرُوا الدُّعَاءَ
The closest a servant is to his Lord is while he is prostrating, so say much supplication then.
Face on the floor is the lowest a body can go, and it is named as the nearest a soul gets. Whatever you want to ask for, ask there.
The full narration
Abu Huraira reported:The Messenger of Allah (ﷺ) said: The nearest a servant comes to his Lord is when he is prostrating himself, so make supplication (in this state)
Source
Ṣaḥīḥ Muslim · 1083
Ṣaḥīḥ
- Agreed upon as authentic (al-Bukhārī / Muslim)