Assalaamu alaykum. I recently came to know about the history of Prophet Uzair, may Allaah exalt his mention, who was brought back to the Children of Israel after 100 years. He then established the rulings of the Torah unto them. My question is: why did he follow the Torah instead of other scriptures that came after it (like the Zaboor)? Is it not mandatory to follow the most recent scriptures and forget about the old ones? I would be very glad if u could answer my question.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallAllaahu ʻalayhi wa sallam, is His slave and Messenger. 

Scholars held different views as to whether ʻUzayr (Ezra) was a Prophet or not. Ibn Katheer wrote, “The famous opinion in this regard is that ʻUzayr was one of the Prophets whom Allaah sent to the Children of Israel...” [Al-Bidaayah wa An-Nihaayah]

Some scholars maintained that the preponderant view in this regard is that ʻUzayr was not a Prophet, such as Abu Hayyaan.

Ibn Katheer said in his book Qasas Al-Anbiyaa' that ʻUzayr was seized by Nebuchadnezzar at a young age. When he reached forty, Allaah bestowed upon him wisdom... and that no one possessed greater or more profound knowledge of the Torah than him.

As for the reason why he did not rule with the Zaboor (Psalms), it was because there were no laws and rulings revealed in the Zaboor. Al-Qurtubi said:

“The Zaboor was a divine book revealed to Prophet Daawood (David), and it contained 150 chapters. It contained no rulings or classification of what is lawful or unlawful; rather, it was confined to preaching and wisdom... Daawood had a beautiful voice so when he recited the Zaboor, humans, jinn, birds and animals used to gather to listen to him. Allaah, The Exalted, says (what means): {And We certainly gave David from Us bounty. (We said): O mountains, repeat (Our) praises with him, and the birds (as well). And We made pliable for him iron.} [Quran 34:10]”

Allaah knows best.