I met Thauban, the freed slave. of Messenger of Allah ﷺ, and asked him to tell me about an act for which, if I do it, Allah will admit me to Paradise, or I asked about the act which was loved most by Allah. He gave no reply. I again asked and he gave no reply. I asked him for the third time, and he said: I asked Messenger of Allah ﷺ about that and he said: Make frequent prostrations before Allah, for you will not make one prostration without raising you a degree because of it, and removing a sin from you, because of it. Ma'dan said that then lie met Abu al-Darda' and when he asked him, he received a reply similar to that given by Thauban.  

لَقِيتُ ثَوْبَانَ مَوْلَى رَسُولِ اللَّهِ ﷺ فَقُلْتُ أَخْبِرْنِي بِعَمَلٍ أَعْمَلُهُ يُدْخِلُنِي اللَّهُ بِهِ الْجَنَّةَ أَوْ قَالَ قُلْتُ بِأَحَبِّ الأَعْمَالِ إِلَى اللَّهِ فَسَكَتَ ثُمَّ سَأَلْتُهُ فَسَكَتَ ثُمَّ سَأَلْتُهُ الثَّالِثَةَ فَقَالَ سَأَلْتُ عَنْ ذَلِكَ رَسُولَ اللَّهِ ﷺ فَقَالَ عَلَيْكَ بِكَثْرَةِ السُّجُودِ لِلَّهِ فَإِنَّكَ لاَ تَسْجُدُ لِلَّهِ سَجْدَةً إِلاَّ رَفَعَكَ اللَّهُ بِهَا دَرَجَةً وَحَطَّ عَنْكَ بِهَا خَطِيئَةً قَالَ مَعْدَانُ ثُمَّ لَقِيتُ أَبَا الدَّرْدَاءِ فَسَأَلْتُهُ فَقَالَ لِي مِثْلَ مَا قَالَ لِي ثَوْبَانُ  

I was with Messenger of Allah ﷺ one night. and I brought him water and what he required. He said to me: Ask (anything you like). I said: I ask your company in Paradise. He (the Holy Prophet) said: Or anything else besides it. I said: That is all (what I require). He said: Then help me to achieve this for you by devoting yourself often to prostration.  

كُنْتُ أَبِيتُ مَعَ رَسُولِ اللَّهِ ﷺ فَأَتَيْتُهُ بِوَضُوئِهِ وَحَاجَتِهِ فَقَالَ لِي سَلْ فَقُلْتُ أَسْأَلُكَ مُرَافَقَتَكَ فِي الْجَنَّةِ قَالَ أَوَغَيْرَ ذَلِكَ قُلْتُ هُوَ ذَاكَ قَالَ فَأَعِنِّي عَلَى نَفْسِكَ بِكَثْرَةِ السُّجُودِ