It's not what we say, it's what Jesus said.
John 3:16 NKJV
16 For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life.
John 3:18 NKJV
“He who believes in Him is not condemned; but he who does not believe is condemned already, because he has not believed in the name of the only begotten Son of God.
Here Jesus mentions believing in the Father as well. You should believe in Jesus, but you should also believe in God.
Life and Judgment Are Through the Son
John 5:24-30
24 “Most assuredly, I say to you, he who hears My word and believes in Him who sent Me has everlasting life, and shall not come into judgment, but has passed from death into life. 25 Most assuredly, I say to you, the hour is coming, and now is, when the dead will hear the voice of the Son of God; and those who hear will live. 26 For as the Father has life in Himself, so He has granted the Son to have life in Himself, 27 and has given Him authority to execute judgment also, because He is the Son of Man. 28 Do not marvel at this; for the hour is coming in which all who are in the graves will hear His voice 29 and come forth—those who have done good, to the resurrection of life, and those who have done evil, to the resurrection of condemnation. 30 I can of Myself do nothing. As I hear, I judge; and My judgment is