'Necessary' in the Bible

For it is not necessary for me to write you about this service to the saints,

Therefore I thought it necessary to exhort the brethren, that they would go before unto you, and make up beforehand your bounty, whereof ye had notice before, that the same might be ready, as a matter of bounty, and not as of covetousness.

If boasting is necessary, I will boast about my weaknesses.

Boasting is necessary. It is not profitable, but I will move on to visions and revelations of the Lord.