Steve Jobs gave Tim Cook advice that guided him as Apple CEO. Now it's Cook's turn to pay it forward.

• Tim Cook has said that Steve Jobs told him never to ask what he would do but "just do what's right."
• Cook now leaves a piece of advice for John Ternus, the incoming CEO of Apple.
• "One of the most important decisions he’ll make is where to spend his time," Cook said.

Steve Jobs once left salient advice for Tim Cook as the Apple cofounder prepared to hand over the reins 15 years ago.

Now, the outgoing CEO has some wisdom to impart to his new successor, John Ternus.

"What I've told him is that one of the most important decisions he’ll make is where to spend his time, and I would spend it where the greatest benefit to the company and the users are," Cook said during Apple's second-quarter earnings call on Thursday.

"And never forget the North Star for the company. We're about making the best products in the world that really enrich other people's lives," Cook added. "And if you keep focusing on that, and make your decisions around that, it will produce a great business, and we'll be able to build more products and do it all over again."

Cook, who will step down as CEO in September, has been at the helm of the Cupertino company since August 24, 2011, replacing Jobs due to the Apple cofounder's debilitating health. Jobs died on October 5, 2011, after battling a rare form of pancreatic cancer.

During a memorial service, Cook revealed that one of Jobs' last pieces of advice to him was "to never ask what he would do. 'Just do what's right,'" Bloomberg reported in 2011.

Cook said at the time that Jobs wanted to avoid the same pitfalls Disney experienced after its founder died and "everyone spent all their time thinking and talking about what Walt would do."

That piece of advice guided Cook throughout his 15-year tenure, the CEO said during the Thursday earnings call.

"Steve's advice to me lifted a huge burden," Cook said. "So that advice did well for me over the 15 years."

Ternus is Apple's senior vice president of hardware engineering and a 25-year veteran at the company who has worked under Cook and Jobs.

"I am filled with optimism about what we can achieve in the years to come, and I am so happy to know that the most talented people on earth are here at Apple, determined to be part of something bigger than any one of us," Ternus said in a statement posted on Apple's blog. "I am humbled to step into this role, and I promise to lead with the values and vision that have come to define this special place for half a century."

Cook will remain at Apple as executive chairman of the board of directors.