Now, leaven represents mixture in its most subtle and penetrating form.
"The Expositor's Bible: The Book of Exodus"
G. A. Chadwick
Jane looked into Athena's face-it was a penetrating, questioning look.
"Jane Oglander"
Marie Belloc Lowndes
Whether his penetrating tones reached the relief party, or whether some person nearer to hand gave the information, does not matter.
"The Man from Jericho"
Edwin Carlile Litsey