From The Hill, yesterday:
Trump said his primary opponents who now refuse to support his candidacy should not be allowed to run for office in the future, since they've gone back on their word….
“Honestly, you sign a pledge, you’re supposed to honor the pledge,” he [said].
From Politico, three months ago:
Donald Trump has rescinded his pledge to support the Republican nominee for president.
Asked during a CNN town hall whether he stood by the earlier pledge — which he signed in September after meeting with party chairman Reince Priebus — Trump said: "No, I don't."