Visuddhimagga VI-52

So taṃ nimittaṃ evaṃ suggahitaṃ katvā sūpadhāritaṃ upadhāretvā suvavatthitaṃ vavatthapetvā sace tattheva bhāvanāpariyosānaṃ pattuṃ na sakkoti, athānena āgamanakāle vuttanayeneva ekakena adutiyena tadeva kammaṭṭhānaṃ manasikarontena sūpaṭṭhitaṃ satiṃ katvā antogatehi indriyehi abahigatena mānasena attano senāsanameva gantabbaṃ.

他如是取相而得善取善把握而善观察已，如在那里（冢墓）修习到最后仍不能得证（初禅），则他回来之时亦如前说的方法单独无伴，于同样的不净业处上作意，置念专注，内摄诸根，意不外向，回到他自己的住所。

Ñ(VI,52): When he has thus properly apprehended the sign, properly remembered it, and properly defined it, then if he is unable to conclude his development on the spot, he can go to his own lodging, alone, in the same way as described of his coming, with no companion, keeping that same meditation subject in mind, with mindfulness well established, and with his mind not turned outwards owing to his faculties being turned inwards.