It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: When any one of you wakes up from sleep, he should not put his hand into a vessel until he has washed it, for he does not know where his hand was during the night.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 7674