How to straighten the rows in Salah?

Q 1: is the command in the following Hadith: “Let those (standing) near to me of you (in congregational prayer) be the mature and the wise.” for obligation or desirability?

A: As for the saying of the Prophet (peace be upon him): “Let those (standing) near to me of you (in congregational prayer) be the mature and the wise.” , it is for desirability and not for obligation. Q 2: What is the proof on straightening the rows (during Salah) and is the Hadith stated for desirability or obligation. What about the following Sahih (authentic) Hadith: “Either you straighten your rows or Allah will cause conflict between your hearts.” Is this threat in return for leaving a Sunnah or for leaving an obligatory act? A: The proof on straightening the rows (during Salah) is mentioned in the saying of the Prophet (peace be upon him): “Either you straighten (Part No. 6; Page No. 325) your rows or Allah will cause conflict between your hearts.” The threat is in return for leaving an obligatory act because the desirable acts do not entail punishment for those who do not do them. Q 4: Can undiscerning children complete the rows, especially the first because Fuqaha’ (Muslim jurists) (may Allah be Merciful with them) arranged the types of people mentioned in the following Hadith: “Let those (standing) near to me of you (in congregational prayer) be the mature and the wise.” into four types as you know. Could you kindly advise? May Allah reward you! A: Salah of undiscerning children is not valid, so it is not proper to place them in the row and they are not counted as filling in the gaps of the rows.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.