We have no meanings for "make an affirmation" in our records yet.
1 And as you think of each thing, make an affirmation to yourself and to the universe:
2 Those who decline the oath may make an affirmation -a declaration, without reference to divine authority, that they will tell the truth.
3 Witnesses will no longer be required to swear before God or make an affirmation when filing affidavits under proposals agreed by Cabinet on Tuesday.
4 Bradlaugh was a frank disbeliever in Christianity, and the House of Commons refused to allow him either to take the oath or make an affirmation .
Grammar, pronunciation and more
This collocation consists of: