Verses with the word swear in the New Testament (12 verses):

Matthew 5:34
But I say unto you, Swear not at all; neither by heaven; for it is God's throne:

Matthew 5:36
Neither shalt thou swear by thy head, because thou canst not make one hair white or black.

Matthew 23:16
Woe unto you, ye blind guides, which say, Whosoever shall swear by the temple, it is nothing; but whosoever shall swear by the gold of the temple, he is a debtor!

Matthew 23:18
And, Whosoever shall swear by the altar, it is nothing; but whosoever sweareth by the gift that is upon it, he is guilty.

Matthew 23:20
Whoso therefore shall swear by the altar, sweareth by it, and by all things thereon.

Matthew 23:21
And whoso shall swear by the temple, sweareth by it, and by him that dwelleth therein.

Matthew 23:22
And he that shall swear by heaven, sweareth by the throne of God, and by him that sitteth thereon.

Matthew 26:74
Then began he to curse and to swear, saying, I know not the man. And immediately the cock crew.

Mark 14:71
But he began to curse and to swear, saying, I know not this man of whom ye speak.

Hebrews 6:13
For when God made promise to Abraham, because he could swear by no greater, he sware by himself,

Hebrews 6:16
For men verily swear by the greater: and an oath for confirmation is to them an end of all strife.

James 5:12
But above all things, my brethren, swear not, neither by heaven, neither by the earth, neither by any other oath: but let your yea be yea; and your nay, nay; lest ye fall into condemnation.