Reference for Kiddushin 41:4

א"ל רב אחא בריה דרבא לרב אשי איכא למיפרך מה למוכר בית בבתי ערי חומה שכן הורע כחו ליגאל לעולם תאמר במקדיש שיפה כחו ליגאל לעולם

Thus!] Let him who sells 'a field of possession' prove it, whose privilege is great, that he can redeem it for ever, and yet he may not borrow and redeem, or redeem half. As for him who sells 'a field of possession', that is because his rights are impaired, in that he [cannot] redeem it immediately. Then let one who sells a house in a walled city prove it.<span class="x" onmousemove="('comment',' He can redeem it immediately, and yet cannot borrow etc.');">⁷</span>

Jastrow