Those posing this question to Jesus were suggesting that he was not old enough to have known Abraham. Jesus answered them that he was indeed much older than 50. He said: "Most truly I say to you, before Abraham came into existence, I have been.” (As a master worker, Jesus had a pre-human existence and was instrumental in the creation of Heaven and Earth)
Proverbs 8:22 - Jehovah produced me as the beginning of his way, The earliest of his achievements of long ago.
John 17:5 - So now, Father, glorify me at your side with the glory that I had alongside you before the world was.
Philippians 2:6, 7 - who, although he was existing in God’s form, gave no consideration to a seizure, namely, that he should be equal to God. 7 No, but he emptied himself and took a slave’s form and became human.
Colossians 1:15-17 - He is the image of the invisible God, the firstborn of all creation; 16 because by means of him all other things were created in the heavens and on the earth, the things visible and the things invisible, whether they are thrones or lordships or governments or authorities. All other things have been created through him and for him. 17 Also, he is before all other things, and by means of him all other things were made to exist,