certify

To attest to (a fact) as the truth.

To authenticate or verify in writing.

To attest that a product, service, organization, or person has met an official standard.

These blankets have been certified as fireproof.

To inform; to tell (a person) that something is true.

Our deeds do us three manners of service. First, they certify us that we are heirs of everlasting life, and that the Spirit of God, which is the earnest thereof, is in us.

To assure (oneself) of something; to ascertain.

After having certified himself of her own good health, he very kindly inquired about her mother and Miss Sophy […].