Reference for Gittin 152:5

ה"ז גיטך כל זמן שאעבור וכו': והא לא עבר אמר רב הונא מאי פניך תשמיש ואמאי קרי ליה פניך לישנא מעליא נקט

they did so in Acco, because it is forbidden for those who live in Eretz Yisrael to go out of it? — Abaye replied: He made two conditions with her, thus: If I reach foreign parts, this will be a Get at once, and if I remain on the road and do not return within thirty days it will be a Get. If he got as far as Acco and returned, so that he neither reached foreign parts nor remained on the road thirty days, his condition is broken.

Jastrow