Tel Aviv district police arrested haredi left-wing journalist Israel Frey on suspicion of incitement to terrorism following a social media post, police confirmed on Wednesday.
On Thursday, the court ruled to extend Frey's detention until at least Sunday.
Israel Police were investigating Frey for expressing joy over the death of the five IDF soldiers in Beit Hanun.
'The world is a better place this morning'
Frey wrote, "The world is a better place this morning, without five young men who participated in one of the most brutal crimes against humanity," during a post on X on Tuesday morning.
"Only in Israel can you both 'oppose' the war and 'be shocked' by what we are doing in Gaza, and also, in the same breath, send heartfelt condolences to those who actually carried out the atrocities. It's very simple: your leniency toward the criminals is indifference toward the crime. And the condolences are the legitimization and fuel for the continuation of the atrocities. Choose a side," Frey added in a second post.
James Genn and Hodaya Ran contributed to this report.