In John chapter 6 verse 28-29, Jesus is asked the question what do we have to do to work the works of God. The verb they use is “ergazomai”, a Greek word meaning to toil or to expend energy at doing something. The noun used is “ergon”, the Greek word from which we get our English word ergonomic, and it means a working occupation invoking effort. So the question Jesus is asked, has been fairly well translated as “what shall we do that we might work the works of God?”.
Jesus then answered them, and said, “this is the work of God that you believe on him whom God sent”. In other words, Jesus referred to believing, as a work. Paul said, “for by Grace are you saved through faith and that not of yourselves it is a gift of God, not of works lest any man should boast”. Now the word “works” that Paul uses is precisely the same Greek word “ergon” as Jesus used. so it seems unarguable, that in the eyes of Jesus and in the teaching of Paul, believing is a work. Note also, that Paul’s statement says you have been saved by grace through faith and that not of yourselves. What is not of yourselves? Everything that went before that statement. That is to say, neither the grace NOR the faith had its genesis in or by you. If the faith was yours, then you are depending on your works to save you, and we all know how fragile faith is. Just look at Peter walking on water, and you get a pretty good idea, of just how faith works. Thank God all the faith that was needed for my salvation and for my redemption was found in Jesus.

A man is not justified by the works of the law, but by the faith of Jesus Christ, Gal 2:16

My faith has found a resting place,
Not in device nor creed;
I trust the Ever-living One,
His wounds for me shall plead.
I have no other argument,
I need no other plea;
It is enough that Jesus died,
And that He died for me.