Well, it’s not like they haven’t done it before. Like in 2024 when they used it on UN Peacekeepers:

By 6 March, the National Council for Scientific Research in Lebanon said 117 white phosphorous bombs had been dropped on southern Lebanon. Israel says that they have been using the substance to create a smokescreen on the battlefield; however, it has been alleged that its use was an attempt by Israel to make the land uninhabitable in the future.

According to a confidential report prepared by the government of one of United Nations Interim Force in Lebanon’s contributing countries that was reviewed by the Financial Times, on 13 October multiple white phosphorus munitions were fired within 100 metres of a UNIFIL base, injuring 15 peacekeepers, after an incident where Israeli Merkava tanks had broken into the base and stayed for 45 minutes.