﴿ قَالَ فَإِنَّا قَدْ فَتَنَّا قَوْمَكَ مِنۢ بَعْدِكَ وَأَضَلَّهُمُ ٱلسَّامِرِىُّ ﴾

“Said He: "Then [know that], verily, in thy absence We have put thy people to a test, and the Samaritan has led them astray."”

Please check ayah 20:89 for complete tafsir.