Shelosha Ve'arba'im Umatayim - mi yodeya?

Question

Who knows two hundred forty-three?

Please cite/link your sources, if possible. At some point at least twenty-four hours from now, I will:

• Upvote all interesting answers.

• Accept the best answer.

• Go on to the next number.

Shabbat Shalom, everyone!

Answer 1

בראשית: יז. ה. ולא יקרא עוד את שמך אברם והיה שמך אברהם כי אב המון גוים נתתיך

אברם = 243

Why was the letter "Hai" added to Avraham's name?

Answer 2

In a non-leap year, Shavuot is the 243rd day in the year if Heshvan and Kislev are both Mele'im (have 30 days):

Tishrei, Heshvan, Kislev - 30 days each
Tevet - 29 days
Shvat - 30 days
Adar - 29 days
Nisan - 30 days
Iyar - 29 days
Sivan - 6 days (Shavuot is on the 6th day of Sivan)