Four Horsemen of the Apocalypse.
A possible answer could be '4 chambers in the human heart'.
4 Phases of the Moon
pH with one hydrogen?
4 equals H a h s o w a w? WHAT IS THE ANSWER
4 S's in Assassin
1 Atomic Weight of Hydrogen
4 to 6 for dinner
4 bushels in a rood
6 wives of Henry the eighth
Should now be 5 T at HA! 5 Terminals at Heathrow Airport
4 Cardinal Points of the Compass
4 and Twenty Blackbirds Baked in a Pie