What do we witness "unto the Father" by being baptized?
2 Nephi 31:10-14
10. And he said unto the children of men: Follow thou me. Wherefore, my beloved brethren, can we follow Jesus save we shall be willing to keep the commandments of the Father?
11. And the Father said: Repent ye, repent ye, and be baptized in the name of my Beloved Son.
12. And also, the voice of the Son came unto me, saying: He that is baptized in my name, to him will the Father give the Holy Ghost, like unto me; wherefore, follow me, and do the things which ye have seen me do.
13. Wherefore, my beloved brethren, I know that if ye shall follow the Son, with full purpose of heart, acting no hypocrisy and no deception before God, but with real intent, repenting of your sins, witnessing unto the Father that ye are willing to take upon you the name of Christ, by baptism--yea, by following your Lord and your Savior down into the water, according to his word, behold, then shall ye receive the Holy Ghost; yea, then cometh the baptism of fire and of the Holy Ghost; and then can ye speak with the tongue of angels, and shout praises unto the Holy One of Israel.
14. But, behold, my beloved brethren, thus came the voice of the Son unto me, saying: After ye have repented of your sins, and witnessed unto the Father that ye are willing to keep my commandments, by the baptism of water, and have received the baptism of fire and of the Holy Ghost, and can speak with a new tongue, yea, even with the tongue of angels, and after this should deny me, it would have been better for you that ye had not known me.