From Sahih Bukhari (Hadith 23):
Narrated Abu Said Al-Khudri: Allah's Messenger (ﷺ) said, "While I was sleeping I saw (in a dream) some people wearing shirts of which some were reaching up to the breasts only while others were even shorter than that. Umar bin Al-Khattab was shown wearing a shirt that he was dragging." The people asked, "How did you interpret it? (What is its interpretation) O Allah's Messenger (ﷺ)?" He (the Prophet (ﷺ) ) replied, "It is the Religion
Reference: Bukhari 23