Charles Ellicott Commentary Psalms 38:16

"For I said, Lest they rejoice over me: When my foot slippeth, they magnify themselves against me." — Psalms 38:16 (ASV)

Lest. —It is better to carry on the force of the particle of condition:

For I said, Lest they should rejoice over me:
Lest, when my foot slipped, they should vaunt themselves against me.