The tweet claimed that the boy was kidnapped by “Israeli settlers, assaulted and thrown in a water well"
The graffiti on the wall of the mosque read, "[They're] destroying the Jews? Kumi Ori will destroy the enemy!"
The Petah Tikvah Magistrate's Court on Monday had already ordered three other suspects released, while extending the prime suspect's detention until Thursday.
“Quiet will be met with quiet, greetings from Komy Uri,” read the graffiti, referring to an outpost near Yitzhar.
Police have opened an investigation into the incident and are gathering evidence and searching for suspects.
There were reports of vandalism to two buildings sprayed with graffiti. One of them said "Muhammad Pig" and the other said "Arabs are enemies to expel or kill."
MK Touma-Sliman: If price tag attackers are ignored, there will be a pogrom on the Palestinians
Price tag attacks were reported in the Palestinian villages of Deir 'Ammar and as-Sawiya and the Arab-Israeli city of Tayibe in which cars were vandalized and an olive tree grove was uprooted.
The incident is being investigated by police as a hate crime.
Jewish residents say IDF protects Palestinians, human rights organizations note uptick in violence against Arabs by settlers.