Translated by John Ireland
http://www.accesstoinsight.org/tipitaka ... ml#iti-072
This was said by the Lord...
"Bhikkhus, there are these three elements of escape. What three? The escape from sensual desires, that is, renunciation; the escape from form, that is, the formless; and the escape from whatever has come to be, from whatever is conditioned and dependently arisen, that is, cessation . These, bhikkhus, are the three elements of escape."
- Having known the escape from sensual desires
And the overcoming of forms,
One whose energy is always ardent
Reaches the stilling of all formations. 
Such a bhikkhu who sees rightly
Is thereby well released.
Accomplished in knowledge, at peace,
That sage has overcome all bonds. 
 Renunciation (nekkhamma) refers here to the first absorption (jhana), which is the entry into the form realm (rupavacara) by leaving behind the realm of sensual desires (kamavacara); it is attained when the mind is "isolated" (vivicca) from sensual desires and other unwholesome states. The "formless" (aruppa) is a formless-sphere meditative attainment. "Cessation" (nirodha) is Nibbana see sutta 51 (Iti 3.2):
 Sabbasankarasamatha: the cessation of all conditioned things, of the whole of conditioned existence; this is Nibbana, the unconditioned state.By fully understand the form element,
Without getting stuck in the formless,
They are released into cessation
And leave Death far behind them.
- Note: The point is not to settle in "form" or in the "formless", which are blissful, and peaceful states attained during meditation, but to realise that they are still subject to impermanence and death. Only in Nibbana is perfect freedom to be found. The attainment of jhana can be such a profound experience that it may easily be mistaken for the ultimate goal. In fact, entire religions and theologies have been founded upon and reinforced by such experiences.
 Teh second verse also appears in Sutta 53 (Iti 3.4)