I searched Bhikkhu Bodhi's translations of the Samyutta Nikaya, Angutarra Nikaya, and Majjima Nikaya, as well as Maurice Walsche's translation of the Dhiga Nikaya. The closest I could come to "incline your mind toward Nibbana" was advice from Sariputta to Anurudda, wherein the latter - who had achieved the jnanas was complaining to the former about encountering obstacles. Sariputta, in Bhikkhu Bodh's translation advises him to "direct your mind to the deathless element."
In a different translation of the same text (by Nyanaponika Thera and Hellmuth Hec ker) Sariputta advises Anuruddha to "direct your mind to the deathless element, Nibbana." AN3:128 / AN3:130.
Since that's as close as I could come to your original quote, I'm afraid I can't be very helpful. However, withing the context of the exchange between Anuruddha and Sariputra, and your question concerning meditation without objects - especially in an Indo-Tibetan Mahayana context I can perhaps be of a little service.
Following Kamalasila, shamatha meditation can be undertaken with an external object, such as a pebble or statue; an internal object, such as the breath or a visualization; or it can be done without an object, in which case it is known as meditation on the essence of things (or shamatha without support). This last type of shamatha is a resting meditation and shouldn't be confused with vipasyana.
Mingyur Rinpoche gives very clear, nice instructions in this technique, as does Thrangu Rinpoche and Dzogchen Ponlop Rinpoche.
On the other hand, it seems that Anuruddha had gained the jnanas of the form or formless realm. In classical Indian texts, one is advised to begin vipasyana prac tice after one has attained the meditative stability of the four formless realms. Various Tibetan teachers have suggested that one can begin sooner - some say as soon as one has achieved the fourth or fifth level of shamatha where the mind no longer strays from the object - no matter how long the meditation session. In any case, one needs strong meditative stability in order for vipasyana practice to be effective.
Traditionally, vipasyana is divided into two parts; analyzing and resting. In the resting stage, one rests in one's realization or certainty, without engaging in further analysis or looking. One may subtly cling to a conceptualization of one's realization, but ideally, this is a sort of formless meditation. Similarly, in tantra mahamudra, one generates the image of a deity, and in the completion stage one dissolves the visualization and - ideally - rests in nonconceptual awareness.
Both sutra mahamudra and Essence mahamudra also entail objectless meditation.
All of which is to say that meditation without an object is indeed a part of the Mahayana path.