Ajwa dates, it is believed come from Jannat and also I have heard, our Prophet (saw) first planted these dates...Here the hadith mentioning ajwa dates..
Ibn Abbas narrated, Rasoolullah (Sallallahu Alayhi Wasallam) has said: أ¢â‚¬إ“The Ajwa dates is from Jannah and in it is a cure from poison (Tirmidhi and Ibne Maja).
Bukahri - Volume 7, Book 65, Number 356, Volume 7, Book 71, Number 663:
Narrated Saud:
The Prophet said, "If somebody takes some 'Ajwa dates every morning, he will not be effected by poison or magic on that day till night." (Another narrator said seven dates).
Also Muslim: Book 023, Number 5081:
Muslim Book 023, Number 5083:
'A'isha reported Allah's Messenger (may peace be upon him) as saying: The 'ajwa' dates of 'Aliya' contain heating effects and these are antidote in the early morning.