Acts 2:15
For these are not drunken, as ye suppose, seeing it is but the third hour of the day.
Cross-references
Acts 2:13
Historical context
Acts 2:13 contains the mockery 'They are filled with new wine' which Peter directly refutes by stating it's only the third hour—providing the immediate context.
1 Thessalonians 5:7
Parallel
1 Thessalonians 5:7 explicitly states 'those who get drunk, get drunk at night,' directly supporting Peter's claim that 9am is too early for drunkenness.