Cairbar asks if Fingal comes in peace, to which Mor-annal
replies: “In peace he comes not, king of Erin, I have seen his forward
spear.” If a stranger kept the point of his spear forward when he
entered a strange land, it was a declaration of war; if he carried the
spear on his shoulder with the point behind him, it was a token of
Telephus æterna consumptus tabe perisset Si non quæ nocuit dextra tulisset opem.
The spear of Telephus could both kill and cure. (Plutarch.) (See Achilles' spear. The heavy spear of Valence was of great repute in the days of chivalry.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894