Above all be of single aim; have a legitimate and useful purpose, and devote yourself unreservedly to it.
Legitimate institutions historically have been defenseless in the face of outright fraud.
The legitimate object of government is to do for a community of people, whatever they need to have done, but cannot do at all, or cannot so well do for themselves, in their separate and individual capacities.
If I put forth a legitimate effort, then I feel like, if that doesn't work out, that's all I can do.
When there are legitimate concerns and frustrations it is never cool to marginalise and ridicule the people who have those concerns.
Prayer is a legitimate expression. Certainly it's not prohibited by the first amendment but protected.
Jihad is holy struggle, a legitimate tenet of Islam, meaning to purify oneself or one's community.