Christ was tempted in the desert. After he had been baptized with the Holy Spirit, the devil came and tempted him. Perhaps the idea of satan was: "I have tempted the first Adam wit success. Now here is the second Adam. I'll try again". But his plans miscarried . When satan, in his last and greatest temptation offered to Jesus the whole world, if Jesus fell down before him only for a moment, our dear Lord Jesus, for the full 100% filled with the Holy Spirit, said "No". He could have said "Yes"and then the catastrophee for us would have been total. You read also, that Jesus after this fight, was very tired and that the angels came to his comfort. If he could not sin, this fight had not made him so tired. Then it would have been only a show.
But from his free will he said: "No"and that was the beginning of always greater blessings for us.
He was tempted all his life long, but without yielding. He was equal to us, he could sin, but he never did.
If it were impossible for him to sin, he would not have been equal to us, but a sort of 'robot'.
You see his human weakness so good in the struggle in Gethsemane, when all the sins of all mankind, from Adam and Eve to the last person, born in 'the thousand years' came to him in that goblet of terror. Then he hesitated for one horrible moment, but the end was a firm "No"to all this hesitation.
When we, his disciples, are full of the Holy Spirit, this glorious moment of 'no sinning' comes also for us.