Surah Az Zukhruf Tafseer

Friends on that Day will be foes one to another except those who have Taqwa.

means, every friendship that exists for a purpose other than for the sake of Allah will turn to enmity on the Day of Resurrection, except for that which is for the sake of Allah, which will last forever.

This is like the statement of Ibrahim, peace be upon him, to his people:

إِنَّمَا اتَّخَذْتُمْ مِّن دُونِ اللَّهِ أَوْثَـناً مَّوَدَّةَ بَيْنِكُمْ فِى الْحَيَوةِ الدُّنْيَا ثُمَّ يَوْمَ الْقِيَـمَةِ يَكْفُرُ بَعْضُكُمْ بِبَعْضٍ وَيَلْعَنُ بَعْضُكُمْ بَعْضاً وَمَأْوَاكُمُ النَّارُ وَمَا لَكُمْ مِّن نَّـصِرِينَ

You have taken (for worship) idols instead of Allah. The love between you is only in the life of this world, but on the Day of Resurrection, you shall disown each other, and curse each other, and your abode will be the Fire, and you shall have no helper. (29:25)

Good News for Those with Taqwa on the Day of Resurrection, and Their entry into Paradise

Allah says,

يَا عِبَادِ لَاا خَوْفٌ عَلَيْكُمُ الْيَوْمَ وَلَاا أَنتُمْ تَحْزَنُونَ