campaign (esp. AmE), election (esp. BrE), manifesto (BrE)
The party's election pledge was to cut income taxes by a third over the next five years.

spending (BrE)
spending pledges given by the government

abstinence, virginity (both esp. AmE)
He took a virginity pledge as a teenager.

give (sb), make, sign, take
fulfil/fulfill, honour/honor
break, go back on, renege on
recite, say
They recited the Pledge of Allegiance. (in the US)

pledge on
manifesto pledges on greater public spending

a pledge of support

Pledge is used with these nouns as the subject:
donor, manifesto

Pledge is used with these nouns as the object:
allegiance, assistance, love, loyalty, obedience, support