The Doctrine and Covenants teaches:
“These are they who are of the terrestrial…Who received not the testimony of Jesus in the flesh, but afterwards received it.” (D&C 76:71,74)
What does it mean to receive “the testimony of Jesus in the flesh”?
Joseph Smith taught:
“First Chapter second Epistle of Peter. The first four verses are the preface to the whole subject. There are three grand Keys to unlock the whole subject. First what is the knowledge of God, Second what is it to make our calling and election sure. Third and last is how to make our calling and election sure. Ans, it is to obtain a promise from God for myself that I shall have Eternal life. that is the more sure word of prophycy. Peter was writeing to those of like precious faith with them the Apostles First to be sealed with the Holy Spirit of promise that is the testimony of Jesus.” (Words of Joseph Smith, p. 209)
If we receive not the testimony of Jesus during this mortal probation, which is to have our calling and election made sure by receiving a promise from God that there is a place prepared for us in the celestial kingdom, the best we can hope for is a terrestrial glory.
How tragic the consequences of underestimating the seriousness of what is required to secure celestial glory.