Hadith: A person who attributes his fatherhood to anyone other than his real father, knowing that he is not his father, commits an act of disbelief. And he who makes a claim of anything which in fact does not belong to him, is none of us, and he should make his abode in Hell. And he who labels anyone as disbeliever or calls him the enemy of Allah while he is in fact not so, his charge will revert to him

عن أبي ذر رضي الله عنه مرفوعًا: (ليس من رجل ادَّعَى لغير أبيه -وهو يعلمه- إلا كفر، ومن ادعى ما ليس له، فليس منا وَلَيَتَبَوَّأْ مَقْعَدَهُ من النار، ومن دعا رجلا بالكفر، أو قال: عدو الله، وليس كذلك، إلا حَارَ عليه).
[صحيح] - [متفق عليه]

Abu Dharr (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "A person who attributes his fatherhood to anyone other than his real father, knowing that he is not his father, commits an act of disbelief. And he who makes a claim of anything which in fact does not belong to him, is none of us, and he should make his abode in Hell. And he who labels anyone as disbeliever or calls him the enemy of Allah while he is in fact not so, his charge will revert to him."
Authentic hadith - Narrated by Bukhari & Muslim

Explanation

This Hadīth contains a severe threat and strong warning for those who commit any of these three acts; so what about the one who commits all of them? The first act refers to someone who knows his real father and is sure about his lineage, yet he denies it and acts as if he doesn't know who his father is and claims that his father is someone else, or ascribes himself to another tribe other than his own. The second act refers to someone who knowingly makes a claim of something that does not belong to him, such as lineage, wealth, a right, a deed, or knowledge. It also includes the person who falsely claims having a particular kind of characteristic and takes advantage of it to draw people's attention to him. Not only shall this person suffers severe punishment, but also the Prophet (may Allah's peace and blessings be upon him) has disassociated himself from him and asked this person to choose his abode in Hell because he is one of its inhabitants. The third act refers to someone who labels an innocent Muslim with disbelief, Judaism, Christianity, or enmity to Allah. Such false charges shall return to the one who makes them, because he is more deserving of these detestable attributes than the Muslim who is free from such accusations.