A more formal or literary variant of 'swear on,' used to invoke something sacred or precious as the foundation of a solemn promise.
To make a very serious promise using something important — like the Bible or your honour — to show you are telling the truth.
2 meanings, ordered from most common to least. Color-coded by CEFR level.
To make a solemn oath, invoking something sacred or revered as a witness or guarantee.
"She swore upon her honour that she would never reveal the secret."
I swear upon my sword / That he is mad.
— William Shakespeare, Hamlet, Act II, Scene 1.
In religious or ceremonial contexts, to formally declare the truth of a statement in the presence of something holy.
"The knight swore upon the cross to protect the kingdom."
To rest a sworn promise upon something valued — placing the weight of the oath on that thing.
To make a very serious promise using something important — like the Bible or your honour — to show you are telling the truth.
More common in older texts, literary writing, religious contexts, and ceremonial language. In modern everyday speech, 'swear on' is preferred. Found in Shakespeare and the King James Bible.
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