What does "11:54:45.241 - Expected BasePart got Tool for Weld:Part0." mean and how do I fix it?

Script:

local player = game.Players.LocalPlayer
local mouse = player:GetMouse()
local rasengan = game.Lighting.Rasengan
local copy = rasengan:Clone()
local toggle = false

mouse.KeyDown:connect(function(key)
    if not toggle and key == "r" then
    rasengan.Parent = player.Character
        local weld = Instance.new("Weld",player.Character["RightHand"])
        weld.Part0 = rasengan -- this is the source of the problem
        weld.Part1 = player.Character["RightHand"]
        weld.C0 = weld.C0 * CFrame.new(0, 0, 0)
        toggle = true
    end
end)

This script is used to equip a tool called rasengan from lighting and every time I try to use it the output says "11:54:45.241 - Expected BasePart got Tool for Weld:Part0."