Consider one of the most famous verses in the Bible:
For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
— John 3:16
(This verse distinguishes between the separate persons of the Father and the Son, so the complications introduced by the Trinity Doctrine can be ignored.)
Jesus (the Son) surrendered his divinity and became a mortal human being:
… he gave up his divine privileges; he took the humble position of a slave and was born as a human being.
When he appeared in human form he humbled himself in obedience to God and died a criminal’s death on a cross.
— Philippians 2:7–8 (NLT)
As a human, he was subject to the same temptations as everyone else.
And as a human, he was also subject to the same penalty for sin.
His undeserved death was so great that it was capable of paying the penalty for all Christians that call upon his name.
This is the most fundamental doctrine of Christianity.
And by living a sinless life, Jesus demonstrated that it is possible for humans to avoid sin (through the help of God's holy spirit that is received after baptism).
People quote John 3:16 all the time, but they don't understand what "he gave" and "perish" really mean.
To "so love … that" indicates that what follows is a risk or sacrifice of some kind, but notice that it refers to God (the Father).
We know how the Son willingly sacrificed and suffered, but what exactly did the Father "give"?
The answer to that is what would have happened had Jesus ever yielded to temptation.
We all know that just one sin would have invalidated his whole purpose for becoming human, but most people don't think about what else it would mean.
Had he sinned, the human Jesus, who "gave up his divine privileges, would have been subject to the penalty of sin.
Following Jesus's physical death, the Father would have been bound by his own Law and would have been unable to resurrect his Son.
Jesus would have perished, remaining permanently dead and no longer having existence as a conscious being.
The Father would then have been left alone, no longer having the Son that had existed with him for all eternity.
That is what they were willing to risk, and that is the sacrifice that the Father gave.
That is a far far more powerful and active love than the passive emotion that most people think John 3:16 refers to.
God's plan for the salvation of mankind required that Jesus risk his own immortality.
So, yes, Jesus was mortal.
Some will argue that no, Jesus never fully gave up his divinity, or that it was impossible for him to sin, but consider what that would mean.
If Jesus couldn't sin, then the Father didn't "give" anything, and John 3:16 makes no sense.
If Jesus was absolutely guaranteed to survive being human and regain his original divinity, then what was the sacrifice?
Do people believe that the Father simply created a charade that made it look like he was risking his Son's life for the love of humanity?
Surely not.