Ersāhā is interpreted in two ways:
1. Ersāhā is used in the sense of fixing / stabilizing, making firm; as in the following verses:
As in:
He irsaʿ the mountains [ersāhā] {that is, He stabilized the earth with mountains so that it would not vanish along with what is upon it}. (al-Nāziʿāt 79:32)
And the rāsiyāt (that is, firm} cauldrons... (Sabaʾ 34:13)
We placed on it/on the earth rawāsī {that is, We left mountains as heavy anchors to stabilize the earth}. (Qāf 50:7)
2. Mursāhā is used in the sense of the time of anchoring / realization; as in the following verses:
They ask you about the Hour, when it will irsaʿ [mursāhā] {that is, when it will anchor / be realized}. (al-Aʿrāf 7:187)
They ask you about the Hour, when it will irsaʿ [mursāhā] {that is, when it will anchor / be realized}. (al-Nāziʿāt 79:42)