וְיָדַעְתָּ֗ כִּ֠י לֹ֤א בְצִדְקָֽתְךָ֙ יְהוָ֣ה אֱ֠לֹהֶיךָ נֹתֵ֨ן לְךָ֜ אֶת־הָאָ֧רֶץ הַטּוֹבָ֛ה הַזֹּ֖את לְרִשְׁתָּ֑הּ כִּ֥י עַם־קְשֵׁה־עֹ֖רֶף אָֽתָּה׃
Kaya alamin mo na hindi dahil sa iyong katuwiran kaya ibinibigay sa iyo ng Walang-Hanggan na iyong Diyos ang mabuting lupaing ito upang angkinin, sapagkat ikaw ay isang bayang matigas ang ulo.
Ibn Ezra
I have explained the word your neck [comment on Exodus 32: 9]. Moreover, the idiom is used here, because he previously had said “you are a stiff-necked people” [9: 6].