Bhaddekaratta Sutta — The Discourse on the Ideal Lover of Solitude
The Discourse on the Ideal Lover of Solitude/An Auspicious Day {M iii 187} In this stirring discourse the Buddha underscores the vital urgency of keeping one’s attention firmly rooted in the present moment. After all, the past is gone, the future isn’t here; this present moment is all we have.

Middle Length Sayings of the Buddha
Long Discourses of the Buddha
Connected Discourses of the Buddha