There are two Suttas that have this phrase, maggo sañjāyati, “the path is born in them”, AN 5.57 and AN 4.170. In one case it’s “as they do so, the path is born in them”, in the other it’s “when they review this subject often, the path is born in them”. In both cases the sentence is followed by “they cultivate, develop, and make much of it”.
I am wondering if these passages could be the place where the later ideas of “reaching the path”, and then the “momentary path”, originated from? The Sutta passages clearly say that after that path has been born, what follows is a period of practice and development. It’s not described as a momentary path that is immediately followed by a fruit.
But what does it mean that a path is born in a person? I am wondering if this somewhat mysterious passage could have led to these equally mysterious explanations of a momentary path and fruit.
Rather than momentariness, it’s much more profitable to focus on penetrating the illusion of continuity in respect to impermanence. This is the long term change perceived in objects which is imperceptible in the immediate, but which can be imposed on it by constant reflection, and which is the true condition of reality. There are exercises for achieving this in the Vism., such as observing the changes in a growing leaf from inception to decline and death.
When the practitioner becomes interested in momentariness or penetrating the illusion of continuity it means they are engaging with the ‘development’ stage of the path as contrasted with the establishment phase, and which is described in the fourth tetrad of Anapanasati and the fourth foundation of mindfulness:
"This is called the frames of reference.
“And what is the development of the frames of reference? There is the case where a monk remains focused on the phenomenon of origination with regard to the body, remains focused on the phenomenon of passing away with regard to the body, remains focused on the phenomenon of origination & passing away with regard to the body — ardent, alert, & mindful — putting aside greed & distress with reference to the world.”
—Samyutta Nikaya 47.40
“When he/she often reflects on this, the [factors of the] path take birth. He/she sticks with that path, develops it, cultivates it. As he/she sticks with that path, develops it and cultivates it, the fetters are abandoned, the obsessions destroyed.”
—Anguttara Nikaya 5.57
“The (factors of the) path take birth” means the establishment phase. It entails familiarization with the individual factors rather than their working together as a functioning dynamic.
That is correct. Magga immediately following phala is not reflected in the EBTs. There is a sutta where a person is said to give dana to only arahantha magga people. If they only lasted a millisecond this would be impossible.
I think it refers to the fruition moment. Meditation masters look for their markers in their students.