The fifth, Shephatiah of Abital: the sixth, Ithream by Eglah his wife.

Wesley's Notes

3:3 His wife - Possibly so called because she was his first, and therefore most proper wife, though her son was born after all the rest before mentioned, and therefore she and her son are put in the sixth place, the wive being here named only for the sons sake.

Jamieson-Fausset-Brown Bible Commentary

3. Eglah his wife-supposed to be another name of Michal, who, though she had no son after her mockery of David for dancing before the ark [2Sa 6:16, 20], might have had one previous to that time. She has the title of wife appended to her name because she was his proper wife; and the mention of her name last probably arose from the circumstance that, having been withdrawn from David and married to another husband but afterwards restored, she had in reality become the last of his wives.

Matthew Henry's Concise Commentary

3:1-24 Genealogies. - Of all the families of Israel, none were so illustrious as the family of David: here we have a full account of it. From this family, as concerning the flesh, Christ came. The attentive observer will perceive that the children of the righteous enjoy many advantages.