The doctor advised that he ... more rest.

Advise, suggest, recommend, insist ইত্যাদি verb-এর পরে that-clause এলে formal English-এ Subjunctive হিসেবে verb-এর base form ব্যবহৃত হয়। তাই ‘The doctor advised that he take more rest’ সঠিক। যেমন: The teacher suggested that he study harder.