וַיְהִ֤י רָעָב֙ בָּאָ֔רֶץ מִלְּבַד֙ הָרָעָ֣ב הָרִאשׁ֔וֹן אֲשֶׁ֥ר הָיָ֖ה בִּימֵ֣י אַבְרָהָ֑ם וַיֵּ֧לֶךְ יִצְחָ֛ק אֶל־אֲבִימֶּ֥לֶךְ מֶֽלֶךְ־פְּלִשְׁתִּ֖ים גְּרָֽרָה׃
And there was a famine in the land, beside the first famine that was in the days of Abraham. And Isaac went unto Abimelech king of the Philistines unto Gerar.
Read halakhic rulings (Jewish law) on Genesis 26:1: and classical halakhic sources.