The Talmud on the Creation of the World with the Letters Yod and Heh

"R. Judah the patriarch asked R. Ammi: What is the meaning of the verse, 'Trust ye in the Lord for ever; for in Yah the Lord is an everlasting rock?' He replied: It implies that if one puts his trust in the Holy One, blessed be He, behold He is unto him as a refuge in this world and in the world to come. This, retorted the other, was my difficulty: why does the verse say 'in Yah' and not 'Yah?' The reason is as was expounded by R. Judah ben R. Ila'i: Yah, he said, refers to the two worlds which the Holy One, blessed be He, created, one with the letter heh and the other with the letter yod. Yet I do not know whether the future world was created with the yod and this world with the heh or this world with the yod and the future world with the heh; but since it is written, 'These are the generations of the heaven and of the earth when they were created' read not 'be-hibare'am' 'when they were created', but 'be-he bera'am', 'He created them with the heh'; hence I may say that this world was created with the heh and the future world with the yod."

-- Talmud Bavli, tractate Menachot 29b