In a report, which mentions the account of Salman’s acceptance
of Islam, we read that Salman’s seller said: “I will not sell Salman,
except for 400 date palms, which put forth 200 yellow dates and 200
red dates.”
The Messenger of Allah (s.a.w.a.) said: “O Ali, gather the date
seeds.” Then he took the seeds from him and sowed them. Then he
said: “O Ali, water them.” Ameerul Momineen (a.s.) watered them.
When the watering was over, trees grew up from the ground. When
the seller arrived and saw that, he said: “I will not sell him till all the
400 trees become yellow.” It happened and he accepted and sold him to the Prophet. It was the Prophet (s.a.w.a.), who named him
Salman
Behaarul Anwaar, vol. 22, p. 359
Isbaatul Wilayah (Part One) – Ayatullah AliNamazi Shahroodi (r.a.)