Proof from the Holy Quran
It is given in Surah Al ‘Imran:
So, her Lord graciously accepted her (Maryam [Mary]) with excellent acceptance and brought her up immaculately and entrusted her guardianship to Zakariyya (Zacharias). Every time Zakariyya (Zacharias) entered her chamber of worship he found with her (novel and uncommon) food items. He inquired: ‘O Maryam, wherefrom have these things come for you?’ She replied: ‘This (sustenance) comes from Allah. Verily, Allah provides sustenance without measure to whom He desires.’ Surah Al-Imran (3:37)
This verse of the Holy Quran explicitly establishes the miracles of the Saints. Hadhrat Maryam (May peace be upon her) is not a Prophet, but a saint. Whenever Hadhrat Zakariya (May peace be upon him) came to her, he would see various fruits near her. In summer, fruits of winter would be found and in winter, fruits of summer.
Out of season fruits and food/sustenance being present without any visible worldly means is the miracle of Hadhrat Maryam (May peace be upon her).