Distinction between Islam (external submission) and Iman (internal faith)

۞ قَالَتِ ٱلْأَعْرَابُ ءَامَنَّا ۖ قُل لَّمْ تُؤْمِنُوا۟ وَلَـٰكِن قُولُوٓا۟ أَسْلَمْنَا وَلَمَّا يَدْخُلِ ٱلْإِيمَـٰنُ فِى قُلُوبِكُمْ ۖ وَإِن تُطِيعُوا۟ ٱللَّهَ وَرَسُولَهُۥ لَا يَلِتْكُم مِّنْ أَعْمَـٰلِكُمْ شَيْـًٔا ۚ إِنَّ ٱللَّهَ غَفُورٌ رَّحِيمٌ

The bedouins say, "We have believed." Say, "You have not [yet] believed; but say [instead], 'We have submitted,' for faith has not yet entered your hearts. And if you obey Allāh and His Messenger, He will not deprive you from your deeds of anything. Indeed, Allāh is Forgiving and Merciful."