كتاب المقدمات
1
The Book of Miscellany
Abu Hurairah (May Allah be pleased with him) reported:
The Prophet (ﷺ) said, "A group of people (both men and women) whose hearts will be like the hearts of birds, will enter Jannah".

[Muslim].

It has been interpreted that such people are those who put their trust in Allah; another interpretation is that these people are tender- hearted.

الرابع‏:‏ عن أبي هريرة رضي الله عنه عن النبي صلى الله عليه وسلم قال‏:‏ ‏ "‏يدخل الجنة أقوام أفئدتهم مثل أفئدة الطير‏"‏ ‏(‏‏(‏رواه مسلم‏)‏‏)‏‏.‏
Arabic/English book reference : Book 1, Hadith 77