Hadith: The Prophet (may Allah's peace and blessings be upon him) said about the Ansār: No one loves them except a believer, and no one hates them except a hypocrite. Allah loves whoever loves them and hates whoever hates them

عن البراء بن عازب رضي الله عنهما أنَّ النبيَّ صلى الله عليه وسلم قال في الأَنصَار: «لاَ يُحِبُّهُم إِلاَّ مُؤمِن، وَلاَ يُبْغِضُهُم إِلاَّ مُنَافِق، مَنْ أَحَبَّهُم أَحَبَّهُ الله، وَمَنْ أَبْغَضَهُم أَبْغَضَه اللَّه».
[صحيح] - [متفق عليه]

Al-Barā’ ibn ‘Āzib (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said about the Ansār: "No one loves them except a believer, and no one hates them except a hypocrite. Allah loves whoever loves them and hates whoever hates them."
Sahih/Authentic. - [Al-Bukhari and Muslim]

Explanation

Al-Barā’ ibn ‘Āzib (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) encouraged love for the Ansār and he made love for them a sign of faith, in order to show gratitude toward the Ansār for their hastening to serve the Message, their support of the religion of Islam, their endeavors to manifest it and shelter the Muslims, their perfect performance in important Islamic matters, their love for the Prophet and his love for them, their offering of their wealth and their lives for him, and their fighting and hostility towards all the enemies of Islam. Indeed, the Prophet (may Allah's peace and blessings be upon him) explicitly stated that it is unimaginable that someone may hate the Ansār except one who does not believe in Allah and the Last Day and is immersed in hypocrisy.