Opening the verse
قَالَ لَقَدْ ظَلَمَكَ بِسُؤَالِ نَعْجَتِكَ إِلَىٰ نِعَاجِهِۦ ۖ وَإِنَّ كَثِيرًا مِّنَ ٱلْخُلَطَآءِ لَيَبْغِى بَعْضُهُمْ عَلَىٰ بَعْضٍ إِلَّا ٱلَّذِينَ ءَامَنُوا۟ وَعَمِلُوا۟ ٱلصَّـٰلِحَـٰتِ وَقَلِيلٌ مَّا هُمْ ۗ وَظَنَّ دَاوُۥدُ أَنَّمَا فَتَنَّـٰهُ فَٱسْتَغْفَرَ رَبَّهُۥ وَخَرَّ رَاكِعًا وَأَنَابَ ۩
[David] said, "He has certainly wronged you in demanding your ewe [in addition] to his ewes. And indeed, many associates oppress one another, except for those who believe and do righteous deeds - and few are they." And David became certain that We had tried him, and he asked forgiveness of his Lord and fell down bowing [in prostration] and turned in repentance [to Allāh].
Scholars differ
Most scholars say the two disputants who climbed into Dawud's prayer chamber were angels sent to test him; some say they were men.
Narrated Mujahid:That he asked Ibn `Abbas, "Is there a prostration in Surat-al-Sa`d?" (38.24) Ibn `Abbas said, "Yes," and then recited: "We gave...So follow their guidance." (6.85,90) Then he said, "He (David ) is one of them (i.e. those prophets)." Mujahid narrated: I asked Ibn `Abbas (regarding the above Verse). He said, "Your Prophet (Muhammad) was one of those who were ordered to follow them