"Then indeed, I announced to them and I confided to them secretly," meaning: I combined my calling them publicly with my calling them privately.
﴿ثُمَّ إِنِّي أَعْلَنْتُ لَهُمْ وَأَسْرَرْتُ لَهُم إسرارا﴾ أَيْ: خَلَطْتُ دُعَاءَهُمْ فِي الْعَلانِيَةِ بِدُعَاء السِّر