So Trump says he has no interests in pursuing Hillary Clinton for whatever crimes she may have committed while Secretary of State.
Candidate Trump may promise prosecutions out the wazoo, but President Trump would be wise to abstain from that process altogether, because it's not his job as President to pursue any specific American citizen for any crimes, nor direct or otherwise influence the Justice Department or the FBI to do so on his behalf. If her crimes rose to the level of a federal indictment, they'll figure that out, Trump need not involve himself in any way.
Dude has a country to manage and instructing the justice department or the FBI to go after Hillary would not only be outside his purvue as President, it would look like a petty, political vendetta for which he doesn't have the time.
As President, he should wash his hands of the Clintons and not be part of whatever Sessions at Justice and the FBI decide to do. And if the investigations don't lead AG Jeff Sessions to indict her, then let her slink out the back door of US politics and mercifully fade away.
Americans have to believe that the FBI and Justice Dept. are apolitical, otherwise the rule of law breaks down.