In the Vimalakirti Sutra (ch. 8: Path to Buddhahood) we read:
"Mañjuśrī then asked Vimalakīrti, “How should the bodhisattva penetrate the path of buddhahood?” Vimalakīrti said, “If a bodhisattva traverses the unacceptable paths, this is to penetrate the path of buddhahood.” [Mañjuśrī] also asked, “How does the bodhisattva traverse the unacceptable paths?” [Vimalakīrti] answered, “The bodhisattva practices the five [deeds of] interminable [retribution] without becoming distraught. ... He manifests acting out of lust ... He manifests the practicing of flattery and deception ... He manifests acting out of the afflictions ... He manifests becoming old and sick ... if a bodhisattva can traverse the unacceptable paths in this way, this is to penetrate the path of buddhahood ... Therefore, you should understand that all the afflictions constitute the seed of the Tathāgata. It is like not being able to attain the priceless jewelpearl without entering the ocean. Therefore, if one does not enter the great sea of the afflictions, one will not be able to attain the jewel of omniscience."
There's also Linji's saying (ch. 21, reference to Lankavatara Sutra 3.58), "Virtuous monks, by creating the karma of the five heinous crimes, you attain emancipation." And this (ch. 22), "Followers of the Way, don’t take the Buddha to be the ultimate. As I see it, he is just like a privy hole. Both bodhisattvahood and arhatship are cangues and chains that bind one. This is why Mañjuśrī tried to kill Gautama with his sword, and why Aṅgulimāla attempted to slay Śākyamuni with his dagger."
As I see it, these Mahayana teachings take the prajnaparamita as the essential realisation of a bodhisattva. Unlike those teachings where they focus on taming the minds of uneducated people (prthagjana), these are meant for those on the bodhisattva vehicle. I find this aspect of the Dharma to be neglected, so many thinks that Mahayana is without deeper teachings and put aside the studying of the sutras only to read the systematised and summarising treatises. That I take as a natural progress just as it's happened with the agamas put aside for abhidharma, and it gives the proper reason for eventually making direct meditation instructions (Vipassana, Pure Land, Zen, Tantra) the living core of the path, while the sutras, in their times, were such instructions too.
"If the Buddha-Nature is seen, there will be no seeing of a nature in any thing."
(Nirvana Sutra, T12n374p521b3; tr Yamamoto)
"Neither cultivation nor seated meditation — this is the pure Chan of Tathagata."
(Mazu Daoyi, X1321p3b23; tr. Jinhua Jia)
“Don’t rashly seek the true Buddha;
True Buddha can’t be found.
Does marvelous nature and spirit
Need tempering or refinement?
Mind is this mind carefree;
This face, the face at birth."
(Nanyue Mingzan: Enjoying the Way, tr. Jeff Shore; T2076p461b24-26)