In Rumi's Masnavi, he writes:
Contrast this good land with that marshy patch
Don't claim this angel and that demon match
When opposites to us appear the same
Like sweet and bitter water, both being clear
Who can discriminate between the two?
None but a man who's tasted truth will do
Magic and Miravles some view the same
For both to them are just a clever game
Magicians challenged Moses, friend of Allah
Producing their own versions of his rod -
The difference is vast, like night and day
Their deeds contrasted, they were poles away!
Their actions earned them curses from the Lord
While Moses earned more grace as his reward
Such unbelievers are apes, no more
Their lying breasts are rotten to the core!
What does Rumi mean by 'tasting truth' here?