Rashi citing Targum Yonasan: I will appoint him the head overseer serving in a lasting place. He translates Ne'eman as lasting - a place that is faithful to those who rely on it, for it will not falter. The verse should be re-arranged - u'Skativ Yased Ne'eman b'Makom.

Radak: This is another metaphor for his grandeur and authority. It will be honor for his entire family; all will be attributed to him, just like a small person is attributed to a great person and relies on him. He is compared to a peg inserted in a strong, lasting place. It is proper to hang anything on it, without fear lest it break or move from its place.

Malbim: His grandeur will be fixed; it will not falter, like a peg inserted in a strong place.