when do you pay mana for a spell? magic

[stu5545]

do u pay the mana for the spell before you cast it or only after and like if it fails because someon used a counterspell do u still gotta pay the mana?

[Alterloth]

You tap your lands and then cast the spell and if it fails then it fails...

[Chodie]

To be completely exact, you tap your source to add mana to your mana pool, then you use the mana from your mana pool to pay for the spell.

[Arix]

You can also tap your lands to add mana as part of casting the spell.