Was it only the 37th year of Yo'ash? It was the 39th or 40th! His father Yehoachaz became king in Yo'ash's 23rd year, and he was king for 17 years! Also, Amatziyah ben Yo'ash Melech Yehudah became king in the second year of Yo'ash ben Yehoachaz Melech Yisrael, and Yo'ash reigned 41 years!
Radak, Malbim: Yo'ash reigned two years in his father's lifetime. After Yehoachaz prayed to Hashem, it says that Hashem heard him (verse 4). How did he know 1 , if not that the salvation began in his lifetime?! However, the salvation was via his son, and not through him. Perhaps a Navi told Yehoachaz to anoint his son in his lifetime, in order to see the start of the salvation.
What is the source that he knew? Perhaps the Navi tells us that Hashem heard him! (PF)
