In The Name of Allaah, The Most Merciful, The Bestower of Mercy
Ibn Manzoor mentions in Lisaanul-‘Arab: [والتَّخْذيل:حَمْلُ الرجل على خِذْلان صاحبه وتَثْبِيطُه عن نصْرته]: At-Takhdheel is when a man betakes to forsaking and abandoning his comrade [friend] and holds back from helping and aiding him.
[ الخاذِلُ: ضد الناصر- Al- Khaadhil is the opposite of an-Naasir (the helper, one who aides you, supports and backs you up)]. So Al-Khadhlaan is when someone forsakes and abandons someone or something. So Ahlul- khadhlaan are those people who forsake and abandon the truth and its people when they need them. [So basically they are yellow bellied turncoats who run away from and leave the people of truth when they most need them]!!! If you look at the verbal noun Takhdeel means: To incite or induce someone from abstaining from, or neglect in aiding, assisting the truth or its people; and also it means to hinder, withhold or prevent from aiding, assisting his companion.
إِن يَنصُرْكُمُ اللّهُ فَلاَ غَالِبَ لَكُمْ وَإِن يَخْذُلْكُمْ فَمَن ذَا الَّذِي يَنصُرُكُم مِّن بَعْدِهِ وَعَلَى اللّهِ فَلْيَتَوَكِّلِ الْمُؤْمِنُونَ
If Allaah helps you, none can overcome you; and if He forsakes you, who is there after Him that can help you? And in Allaah (Alone) let the believers put their trust. (Surah Aali Imran 3:160)
يَا وَيْلَتَى لَيْتَنِي لَمْ أَتَّخِذْ فُلَانًا خَلِيلًا لَقَدْ أَضَلَّنِي عَنِ الذِّكْرِ بَعْدَ إِذْ جَاءنِي وَكَانَ الشَّيْطَانُ لِلْإِنسَانِخَذُولًا
“Ah! Woe to me! Would that I had never taken so-and-so as a friend! He indeed led me astray from the Reminder (this Qur’aan) after it had come to me. And Shaitaan (Satan) is ever a deserter to man in the hour of need.” (Surah Al-Furqan 25:28-29)
Translated by Abu Abdillaah [Bilaal Husayn]