Rousing Refrain in hand or in exile with at least one time counter on it.An opponent has at least seven cards in hand.
({3} magic symbol) ({R} magic symbol) ({R} magic symbol) if Rousing Refrain is in your hand, or ({7} magic symbol) available otherwise available.
Steps
If Rousing Refrain is in your hand, cast it by paying ({3} magic symbol) ({R} magic symbol) ({R} magic symbol) .
Otherwise, activate The Tenth Doctor by paying ({7} magic symbol) , causing you to time travel three times, removing all time counters from Rousing Refrain and cast Rousing Refrain from exile without paying its mana cost.
Resolve Rousing Refrain, adding at least seven ({R} magic symbol) , and exiling Rousing Refrain with three time counters on it.
Repeat from step 2.
If an opponent has eight or more cards in hand, this combo nets infinite red mana.