Albert Barnes Commentary 1 Samuel 10:2

"When thou art departed from me to-day, then thou shalt find two men by Rachel`s sepulchre, in the border of Benjamin at Zelzah; and they will say unto thee, The asses which thou wentest to seek are found; and, lo, thy father hath left off caring for the asses, and is anxious for you, saying, What shall I do for my son?" — 1 Samuel 10:2 (ASV)

How was Saul to know that what Samuel said was the word of the Lord? Samuel gives him a sign: You will find two men... (Isaiah 7:11–14; John 6:30; Mark 11:2; Mark 14:13, etc.).

Zelzah - A place absolutely unknown.