You have no right to ask someone to commit a murder, obviously, but it's hard to say if the First Amendment protects the right to extol or encourage murder - not just murder in general but the murder of a person, or class of people, in particular. Advocacy of violence is protected speech (prohibitions on advocacy inevitably restrict unpopular political speech, as early and mid 20th century red scares demonstrated.) Conversely, neither incitement to violence nor "true threats" of violence ("where the speaker means to communicate ... intent to commit an act of unlawful violence to a particular individual or group ...") are, in theory, constitutionally protected; but, in practice, courts still struggle to define and distinguish between incitement, threats, and mere advocacy.
The state courts of Texas will get another chance in a lawsuit filed by Michael Weinstein, founder of the Military Religious Freedom Foundation (MRFF) charging that imprecatory prayers (that Weinstein's "days be few") and "virulent" anti-Semitic "rants" against him constitute "terrorist threats," proscribed by Texas law. Weinstein alleges that Elmer Ammerman, founder of the Chaplaincy of Full Gospel Churches (CFGC) and his associate, Gordon Klingenschmitt, issued an effective fatwah against him (along with Barry Lynn, executive director of Americans United for Church and State.) You can find the offending prayers, offered by Klingenschmitt, here. They include this plea:
"Let us pray. Almighty God, today we pray imprecatory prayers from Psalm 109 against the enemies of religious liberty, including Barry Lynn and Mikey Weinstein, who issued press releases this week attacking me personally. God, do not remain silent, for wicked men surround us and tell lies about us. We bless them, but they curse us. Therefore find them guilty, not me. Let their days be few, and replace them with Godly people. Plunder their fields, and seize their assets. Cut off their descendants, and remember their sins, in Jesus' name. Amen."
Weinstein plausibly claims that as a result of Ammerman's tirades and the curses rained upon him by Klingenschmidt, "threats and hate mail (against Weinstein and his family) have increased exponentially; (they) justifiably live in fear of imminent violence..."