Is what is stated in the Hadith that Muhammad agreed with the Rabbi's opinion or vice versa, and is the addition "تصديقًا له" (as a confirmation to him) authentic?

The addition, "confirming him," is established in the narration by the two Sheikhs (Bukhari and Muslim) of the hadith (definition) concerning the Jewish scholar who described the Day of Resurrection. The meaning of the hadith is that the Prophet, peace and blessings be upon him, confirmed the scholar and affirmed what he described regarding the Day of Resurrection, out of wonder and confirmation of Allah's power, not out of seeking knowledge from him. He then recited the verse that supports this: {And they did not appraise Allah with true appraisal...}