Acts.25.7  And when he had come, the Jews who had gone down from Jerusalem stood about him, bringing against him many serious charges which they could not prove.
1Tim.3.8  Deacons likewise must be serious, not double-tongued, not addicted to much wine, not greedy for gain;
1Tim.3.11  The women likewise must be serious, no slanderers, but temperate, faithful in all things.
Titus.2.2  Bid the older men be temperate, serious, sensible, sound in faith, in love, and in steadfastness.

Hyper-concordance v1.1, by Sean Boisen. Scripture verses taken from the Revised Standard Version, copyright 1952, 1971.