From Sahih Bukhari (Hadith 2809):
Narrated Anas bin Malik:Um Ar-Rubai' bint Al-Bara', the mother of Haritha bin Suraqa came to the Prophet (ﷺ) and said, "O Allah's Prophet! Will you tell me about Haritha?" Haritha had been killed (i.e. martyred) on the day of Badr with an arrow thrown by an unidentified person. She added, "If he is in Paradise, I will be patient; otherwise, I will weep bitterly for him." He said, "O mother of Haritha! There are Gardens in Paradise and your son got the Firdaus al-ala (i.e. the best place in Paradise)
Reference: Bukhari 2809