most requisite

You, Hortense, who used to be so good, should continue so now, when it is most requisite.

From Hortense Makers of History Series by John S. C. (John Stevens Cabot) Abbott

In the parts where shelter was most requisite, two-thirds of fir and one-third of oak were planted, in others half of each, and in sheltered situations oak alone. 

From The Forest of Dean An Historical and Descriptive Account by H. G. (Henry George) Nicholls

Lastly the said master shall not bygynne to teache or dismisse the said Schoole without convenient prayers and thankesgyveinge, in that behalfe publiquely to be used, most requisite att bothe mornynge and evenynge.

From A History of Giggleswick School From its Foundation, 1499 to 1912 by Edward Allen Bell

I shall not venture to pronounce what, among the multitude of talents that are requisite to constitute a good librarian is the most requisite.

From A Book for All Readers An Aid to the Collection, Use, and Preservation of Books and the Formation of Public and Private Libraries by Ainsworth Rand Spofford

This understanding is most requisite in a Prince, inasmuch as the whole Globe is in his hand, and the inferiour Orbes are swayed by the motion of the highest.

From Machiavelli, Volume I by Edward Dacres