The disciples answered Prophet Jesus (PBUH) by saying:
“Firstly: It will be our provision which we want to eat from.
Secondly: We will get reassurance by looking at the way it was sent down.” Thus, it would strengthen their faith.
( وَنَكُونَ عَلَيْهَا مِنَ الشَّاهِدِينَ… ) (…and be among its witnesses.”): i.e., it will serve as a miracle for everyone which we have become witnesses for.