once
وَقَالَ صلى الله عليه وسلم: ((أَقْرَبُ مَا يَكُونُ الْعَبْدُ مِنْ رَبِّهِ وَهُوَ سَاجِدٌ فَأَكثِرُوا الدُّعَاءَ)).
Meaning
He also said: ‘The nearest a servant is to his Lord is when he is prostrating, so supplicate much therein.
Source and references
Hisn al-Muslim, entry 252.The reference is copied from the edition; separate editorial verification is not complete yet.
Source edition: Fortress of the Muslim. Open source ↗