Exegesis:

ho de emblepsas autois eipen ‘he looked at them and said.’ emblepsas (also 22.61) denotes a meaningful look; the verb is often used to introduce an act of special meaning, cf. e.g. Mk. 10.21.

ti oun estin to gegrammenon touto ‘then what does this text of Scripture mean?’ oun is inferential and means, ‘if you don’t want this to happen,’ cf. Plummer. to gegrammenon lit. ‘that which is written,’ hence ‘text of Scripture.’

Translation:

He, or, ‘Jesus.’

Looked at, or, ‘fixed-his-eyes-on’ (Tae’), ‘observed-closely/intently’ (Bahasa Indonesia RC).

What then is this that is written, i.e. how then do you explain/interpret/understand this text?. For this that is written cf. on “the place where it is written” in 4.17.

Builders, or, ‘those who build/make the house.’

The head of the corner, or, “the main corner-stone” (New English Bible), ‘the post of the corner’ (Javanese), ‘the stone that-strengthens the corner of the wall’ (Balinese). Some renderings make use of cultural equivalents, e.g. ‘principal stone’ (Toraja-Sa’dan, employing the name of the big stones on which the main poles of a house are erected), ‘stone which combines the house’ (Kipsigis in 1 Peter 2.6, in analogy to the term for the centre pole of the hut), ‘the root of the house at the corner’ (Kekchi), ‘stone heavy pole’ (Tae,’ qualifying ‘stone’ by the term that refers to the four big corner-poles of a house), ‘the main pole’ (Aguaruna, without any reference to a stone, since stones are never used in the region for the building of a house). Some descriptive renderings used are, ‘place/thing-where-the-house-corner-receives-strength’ (Tzeltal), ‘the chief stone that carries the whole house’ (Sranan Tongo), ‘the thing joining the walls’ (Shona 1966).

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.