What David could not do: David could not undo what he had done. And he could not escape the consequences of his mistakes.
مَا لَمْ يَسْتَطِعْ فِعْلَهُ :‏ لَمْ يَقْدِرْ دَاوُدُ أَنْ يَرْجِعَ بِٱلزَّمَنِ إِلَى ٱلْوَرَاءِ وَيُصَحِّحَ خَطَأَهُ .‏