בראשית לח:יא פירוש: רש״י, רמב״ן, ספורנו ורד״ק

‘כי אמר וגו FOR HE SAID etc. — that is to say, he pushed her off with a straw (i.e., he put her off with a lame excuse) because he never intended to give her to him in marriage

ABIDE A WIDOW AT THY FATHER’s HOUSE. The meaning thereof is that “you should conduct yourself there as a widow until Shelah be grown up.” He suggested to her: “Place yourself in mourning, put on mourning garments, do not anoint yourself with oil, as a woman girded with sack-cloth for the bridegroom of her youth,¹⁶⁵Joel 1:8. until Shelah be grown up and he will marry you.” Such was the custom of a widow waiting to be married: she who desires to be married to a stranger wears mourning garments only for a short period as is the custom, and then feigning comfort arrays herself in scarlet. And she covered herself with a veil,¹⁶⁶Verse 14 here. Ramban thus interprets the verse; And she removed the garments of her widowhood, and covered herself with a veil, as an indication that she was no longer mourning. See Ramban further, Verse 16. until she be married to a man.

שבי אלמנה, wait for a while in a state of widowhood. This expression also occurs in Hoseah 3,3 ימים רבים תשבי לי, “you will have to go a long time without marrying.”