Resuming Sleep After Interruption and Still Regaining Daily Use Abilities

[Endarire]

EDIT: Rules Compendium 128 and 129 mentions this separately for arcane and divine spell preparation.

Greetings, all!

I recall reading somewhere official (web article?) that characters, if interrupted mid-sleep, could still return to sleep and recover their daily use abilities like spells. What is the rule/ruling and source?

I'm NOT seeking abilities that reduce the amount of time needed to recover said abilities like a Heward's Fortifying Bedroll (Complete Mage 132).

Thankee!

[Covenant12]

The Player's Handbook, page 178 "Rest:" explains it fairly thoroughly. Interruptions add an hour, 1 hour at end to be able to memorize spells.

Note that Clerics and Druids don't have to sleep ever. They have a certain time of day they can memorize spells or not, interruptions are fine if you attempt to memorize spells ASAP.