Yājñavalkya Śikṣā 213

213

apañcamaiścaikapade saṃyuktaṃ pañcamātparam
utpadyate yamastatra so'ṅgaṃ pūrvākṣarasya

In a single word, when [a consonant] is joined by non-nasals and followed by a nasal,
a yama nasal arises there; it forms a part of the preceding syllable.